On Tuesday, the 37th BlackBerry to have been produced arrives on these shores.

The device has already cemented its place as the indispensible accessory of deal-makers the world over. But as Apple and others, notably Nokia, beat down the door, does RIM, the company which makes it, have any tricks up its sleeve for the 8820, the latest in its stable?

Well, not really. The 8820's most significant point of distinction is that it is wi-fi enabled, a function which will arguably be of limited use to most. This doesn't reflect any lack of innovation on RIM's part, though.

The 8820 - which is out first on Orange, with other networks to follow - shows that, having built up an immensely loyal subscriber base of nine million with its push e-mail service, RIM can now afford to tailor new BlackBerrys to niche markets. In this case, it's 'the highly mobile worker' as opposed to, say, 'the woman who wants her BlackBerry to look more like a phone'.

To start with the basics: the 8820 is a slightly chunkier device, more in the old BlackBerry style, weighing 134g as compared with its predecessor, the 111g Curve.

The now familiar trackball mechanism, which allows for left/right navigation as well as up/down, is again in evidence, suggesting that RIM has completed the move away from the side-scroll wheel of earlier models, and the keys on the QWERTY keyboard are slightly bigger than the Curve's, which makes them more forgiving of fatter thumbs.

The wi-fi capability, which is increasingly common on smartphones, will probably only excite those who frequently use their phone in areas with poor reception and easy-to-find hotspots – arguably not the most common type of geography – and the GPS facility will be of most help to those same people.

(An informal survey of BlackBerry users conducted by Times Online suggested that even in the home, where the 8820 will be able to piggyback on a broadband wireless connection and download more quickly, the wi-fi won't be of great use. "I wouldn't know a wi-fi zone if it jumped up and bit me," one veteran user said.)

The GPS function, on the other hand – which will be familiar to owners of the 8800, the new model's closest cousin – has been known to get the odd stray suit to a meeting.

Significantly, the browsing experience is not nearly as good as on the Curve or other more consumer-focused models. YouTube, for instance, loads pretty poorly, as do several other 'rich media' sites with lots of video, such as Apple's. There is also no camera.

RIM, which according to Gartner has just under 20 per cent of the PDA market, says this is because the 8820 is not aimed at consumers; those who want to combine the core competency of BlackBerry – push-email – with the more traditional features of the smartphone – a good browser, camera, music player etc – would be well advised to go for the Curve or its even thinner predecessor, the Pearl.

In truth what it shows is that manufacturers of smart phones are now presented with a problem. All the bits that do the whizz-bang stuff – the GPS, wi-fi, the camera with lots of mexapixels, the smart music player and so on, are available. They're just too expensive – and bulky – to put in one device.

So if you're RIM – or any of its competitors, such as Nokia, which has muscled in with its N series recently – you focus on a few features, and get your sales teams to plump for them.

In the 8820's case, RIM is targeting the mobile worker who could do with help navigating, and whose network isn't always the most reliable. In other words, a salesperson careering around the shires, rather than the office worker in St Paul's.

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