Errant teenagers will regard them with horror, but for parents, location tracking services designed to keep tabs on their offspring can give peace of mind. The technology enables parents to log on to the internet and then – in theory at least – view their child’s location on a web-based map. There are at least five such systems on the market but little information about how well they work, or if they work at all.

The services fall into two categories: one pinpoints a child’s location by using the network of mobile phone masts that cover most of Britain. The other relies on the same type of GPS receivers commonly employed by sat nav systems.

The systems based on the mobile phone network (known as GSM-based) don’t require any extra gadgets and work with most handsets but not every service provider. The tracking company sends a signal to the designated phone, which responds with its own signal giving the user’s location.

However, you can forget any Mission: Impossible notions of precise real-time tracking – these services are only as good as the phone networks. The greater the density of masts, the more precise the location track should be. Some services claim a precision of up to 100 metres, but in urban tests the best we achieved was to locate our target within a 900-metre zone.

In rural areas, where masts are sparse, these GSM services were even less useful at locating a target precisely and some gave entirely the wrong location. The ChildLocate system claimed the phone bearer was within 3,615 metres of Washaway in Cornwall when she was over 4km away.

The GSM-based service from FollowGB (not to be confused with the GPS package from the same company – also reviewed) said the bearer was within 4.8km of the map’s epicentre when she was 10km (6.2miles) away.

Another drawback is that GSM-based tracking doesn’t work if the phone is switched off. And most services do not cater for customers of the Virgin Mobile, BT Mobile or 3 networks. All the services are at least fairly cheap.

You can opt to pay a monthly subscription of around £15 or buy “tracking credits” on a pay-as-you-go basis where each track costs around 40p.

The GPS-based systems we tested were, on the whole, much better than their GSM rivals. They were precise to within 10 metres and, unlike the phone-based systems, never showed the target to be somewhere it wasn’t. Unlike mobile-based systems you must first buy a dedicated device fitted with a GPS receiver typically costing £200. This signals its position via geostationary satellites.

The websites of these services offer more sophisticated features, including the ability to define an area within virtual geofences (see jargon buster) such as around a school. Once you have done so, you receive an SMS text alert if your child enters or leaves the area.

This could also be useful for elderly relatives suffering from dementia.

The shortcoming of GPS receivers is that they can work poorly indoors unless close to a window and are adversely affected by trees, tall buildings, or poor weather. The other main difference between the GPS and GSM systems is that the latter require administrative hurdles to allay privacy concerns. Under Home Office guidelines you (the parent) must first establish your identity upon signing up by agreeing to online payment card checks. Then a Pin number is sent by post. The person being tracked must also give their permission by replying to a text sent to their phone. A parent can answer for their child. After that, the holder of the phone will receive intermittent SMS texts reminding them they can opt out.

JARGON BUSTER

Bluetooth Short-wave radio tool that enables some gadgets to work wirelessly in tandem with a Bluetooth-enabled mobile phone

Geofences Most GPS-based tracking services enable subscribers to designate areas on a map called geofences. If the holder of the GPS gadget enters or exits one of these areas, an SMS text alert is sent to the subscriber

GPS (Global positioning system) Navigation technology that relies on satellites

GSM (Global system for mobile communication) Underlying infrastructure employed by the mobile phone networks in Europe

Reviews by Matthew Wall. Prices include Vat

SATELLITE OF LOVE

FollowGB www.followgb.co.uk

Decent tracking features despite rough edges

Unless you own a compatible smartphone, this service requires you to buy its Person Locator GPS gadget for £234. With it you get 50 “tracking credits”. One credit is used up each time you check its location. These are subsequently sold on a pay-as-you-go basis and cost from £23.50 for 50. The gadget is small and quite stylish, with SOS alert buttons. It also doubles as a basic mobile phone. All GPS receivers tend to be disrupted when there is no “line of sight” between them and the satellites they communicate with, which means they often stop working when indoors. The Person Locator was no exception and worked only intermittently indoors. However, it proved to be precise to within a few yards. You can view the gadget’s whereabouts via the company’s website using Multimap, Microsoft MapPoint, or indeed Google Earth. The software was clunky but it did work and it is also possible to set up geofences, such as around a child’s school, either on the website or the gadget itself. A GSM-based tracking service is available from the same company, although this was not on test.

SIMPLE SIMON

Findware www.findware.co.uk

Effective GPS-based service that isn’t consumer-friendly

To use the Findware service you must first purchase a GPS tracking receiver called the GT2000 (the company plans to add to its range of receivers). The price of this gadget varies from £99 to £199 on an annual contract basis, depending on monthly subscription costs, which start at £14 per month. The iPod-sized GPS device located our target to within 10 metres. Better still, the Findware receiver maintained a lock on the satellite while inside a schoolbag, and indoors, providing this was no more than a few metres from a window. It could be traced as it moved from home to school on a website using Microsoft MapPoint maps (not as good as Multimap or Google Earth). Geofences can be set up to alert parents when their child strays outside or into a defined zone. To do so involves logging on to the company’s website. Rival GPS trackers reviewed here allow geofences to be created using the actual receiver itself. As a phone, the GT2000 is extremely basic: there’s no screen, and although it can handle incoming voice calls, it only allows you to store three numbers for outgoing calls. Nevertheless, it’s a credible option.

SOS FOR KIDS

BestBuddy (www.buddysafe.com )

Clever child-alert system but poor tracking features

This not-for-profit service is co-marketed by the charity Bullying Online and enables children to alert a parent or carer discreetly if they need help, though it does have GSM-based tracking features too. The service is based around a special Bluetooth keyfob that is supplied free for children. Once this is partnered with a Bluetooth phone, one press of the keyfob’s button orders the phone to send an SOS message to preselected adults via SMS text, email and voicemail. Parents can also view the child’s location on a website-based map. This is a good idea, yet setup proved fiddly. Pairing the keyfob with a mobile phone involved unscrewing and removing the back of the unit and then keeping the alert button pressed while inserting the battery. In urban tests, conducted with a Vodafone sim card, alerts were received promptly. However, the system pinpointed the location only to within a radius of 1.2 miles, so you would have to hunt over a wide area to find a lost child. The subscription for the first month costs £10, and is then charged at £5 per month thereafter. Location requests and voice messages cost 15p, text alerts 10p and emails are free. Limited use for tracking, then, but a good-value alert system.

AGENT PROVOCATEUR

Trace a Mobile (www.traceamobile.com )

Mobile phone-based service that works, but barely

This GSM-based tracking service works with most mobile phones but in tests it proved inaccurate. At one point it said the phone bearer was within 800 metres of a local railway station – which is unhelpfully imprecise in the first place – but she was in fact at home, some 1,200 metres from the station. It claimed a narrower search radius than its GSM rivals (Trace a Mobile claims this can be as low as 50-100 metres in towns) but the best we managed was to pinpoint a target within 924 metres. The service costs £5.87 a month for a (minimum) six-month subscription, or £58.75 on an annual basis. This includes 10 tracking credits a month, after which 30 credits cost £10.50. The registration process did not inspire confidence. Instead of posting you a physical Pin number, as Home Office guidelines recommend, to protect privacy, you can instead just sign up online. An activation password was then sent to the test phone, which was on the Orange network. Once this password was entered into the company’s website you could immediately begin using the service. Another downside was that the company’s telephone-based technical support cost a steep £1 per minute – and the phone number didn’t work.

SPATIAL DISLOCATION

ChildLocate (www.childlocate.co.uk )

Limited GSM-based service that’s flaky at best

The nicest thing to be said for ChildLocate (which also markets itself as MobileLocate) is that this GSM-based service offers a 30-day free trial, and that’s long enough to establish its faults. A phone was registered and then activated on the O2 network, which is compatible with ChildLocate. However, despite several attempts, the service did not manage a single successful track in our initial city-based tests. The mobile had good reception, yet still no dice. To make matters worse, the website’s help section proved anything but helpful. Eventually, the technical support line said that the servers had gone down. The testing was repeated, this time with a T-Mobile phone, and we did get a result, which said the handset was located within 2,026 metres of Bermondsey Tube station. Saying that a child is within a 2km (1.2mile) radius of something isn’t going to be good enough for most parents. ChildLocate claims it can narrow the location to a radius of 150-400 metres in built-up areas, but that was not our experience. The annual service charge is £70 and this includes an initial 25 tracking credits. These credits are then sold on a pay-as-you-go basis priced from £5 for 33 credits, which equates to 45p per track.