By Alfred Hermida BBC News Online technology editor

The Blackberry lets you receive your e-mails wherever you are

It has become the must-have gadget for the high-powered executive who cannot bear to be away from their e-mail.

Among the fans is the Easy group founder, Stelios Haji-Ioannou, who uses Blackberry to check his e-mails before he has even got out of bed.

More than a million people across the world are using this hybrid device, which lets you receive and send e-mails on the move.

It has proved particularly successful in the US, which has not made much use of SMS text messages.

But the Blackberry has been slow to appeal to Europeans, who have embraced texting as the way to keep in touch.

The figures speak for themselves. By the end of November last year, just some 100,000 Blackberry subscribers were based outside North America.

Serious handheld

The wireless capability is the Blackberry's ace in the hole. Using it for e-mails is a cinch, thanks to its built-in qwerty keyboard. The keys are on the small size but typing is relatively painless.

Messages are automatically sent and received to the device so you need never be out of touch.

The device works well as a phone

There are several Blackberry models on the market. One of the most popular is the 7230, which has a high-resolution screen with a 250x160 display that can present over 65,000 colours.

The latest model is the Blackberry 7730, which has been described as the 7230's big brother.

It is slightly bigger and has a larger, 16-bit colour screen capable of displaying four rows of icons rather than the 7230's three.

Navigating the icons is done by a scroll wheel on the side and there is a handy back button just next to it.

Both handhelds have 2MB of SRAM and 16MB of Flash memory but no memory card expansion slot.

As a phone, the quality of the calls on the 7230 is surprisingly good, though it does feel odd holding the chunky device to your ear.

And busy people on the move will be pleased with the gadget's battery life. It is intended to last for up to four hours of talk time and 10 days of standby time.

Used sparingly, you could even go a week without needing to recharge the device.

The address and calendar programs are nothing special. They do the job but are not quite as flashy as those on a smartphone.

And for those looking to use it as an entertainment device will be disappointed, with no music or video playback. After all, this is a device for business not pleasure.

Smart challenges

As a gadget, the 7230 is a triumph of function over style. It may sound superficial, but it does look rather ugly and bulky.

BLACKBERRY 7230 Weight: 4.8 oz (136g) Backlit Qwerty keyboard 65,000 colour display 16MB flash memory plus 2MB SRAM Tri-band: 900/1800/1900 MHz

In terms of style, it fares badly against the likes of Sony Ericsson's P900 and Orange's SPV E200.

These are just two of the hybrid devices currently available that combine a handheld computer with a mobile phone and can do all the things a Blackberry does and more.

Interestingly the company behind the Blackberry, Research In Motion, (Rim), is looking to offer its service on these types of devices.

At the end of February, it announced that its Blackberry communications service would be available for Sony Ericsson phones later this year, starting with the P900.

Rim has made similar agreements with Nokia and Samsung.

Anyone can walk into a mobile shop and pick up a Blackberry which can be set up to work with your home e-mail.

But Rim is really aiming its messaging service at large companies where e-mail plays a crucial role in doing business.