T-Mobile has had a great deal of success with its range of connected Windows Mobile Pocket PCs. This has been in part due to very user-friendly pricing on contract tariffs, and in part due to its partnership with ALK and specifically with that company's CoPilot navigation software. The partnership continues with the new MDA Compact III, available either with or without CoPilot.

The advantage of the MDA Compact III over earlier devices in the range, as far as navigation is concerned, is that it has a built-in GPS antenna. This means you do not need to charge or carry a separate antenna or indeed to go through the hassle of pairing an antenna over Bluetooth with the MDA Compact III. You simply choose to run the software when you need to.

Even without the CoPilot - or any other - navigation software, the MDA Compact III is an impressive piece of kit. It is small, thin and light (58mm x 108mm x 16mm and 160g) and styled in a compelling grey.

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What immediately impresses in the first few minutes of use is the fact that this handheld dispenses with a navigation button and instead offers a combination of wheel and mini trackball. The mini trackball is an idea we've seen recently in the BlackBerry Pearl. You roll it under the thumb to move around within the screen, and press to make selections. It is illuminated by a gentle blue backlight when in use.

The wheel is an idea taken from portable music players. Again it provides a scrolling function and it feels much more comfortable under the thumb than any PDA navigation button or mini joystick we have used.

There are some omissions, though. While the MDA Compact III has Bluetooth it lacks Wi-Fi. While it has a 2-megapixel camera it lacks a miniature flash unit. While it quite naturally enough supports T-Mobile's Web'n'walk Internet access, with its home page offering a Google search area and links to a range of useful Web sites, it is not a 3G device.

Windows Mobile Pocket PC Phone Edition has been supplemented with an FM radio which can be used for entertainment purposes along with the Windows Media Player, and a microSD card can be used to add to the built-in memory, though irritatingly you need to remove both battery and SIM card to get to its slot.

The feature mix in the T-Mobile MDA Compact III is frustrating. The device is neat and pocket-friendly, and it covers the Pocket PC basics extremely well. We love the wheel and mini trackball. But without Wi-Fi or 3G it is less useful than it should be.