Trendy handheld Blackberry devices could cause damage to users' thumbs, doctors are warning.

Sales of the £200 gadget, which can be used to email, page and phone, have boomed in recent years with celebrities such as David Beckham using them.

But US and UK doctors said repetitive use could cause arthritis or harm tendons in the thumb.

Research in Motion, which manufactures the Blackberry, said it would not comment on the claims.

I'd heard the word but hadn't bothered to look to see what a Blackberry was until I read this post. Cute little thing but it'd be of no use to me. The only time I'm away from a keyboard is when I'm in my car. I did the laptop-cellphone connection thing while away from home or office at one point. If I ever needed to be that tied to a computer again I'd get the wireless service that's being pushed these days.

A good alternative to repetitive stress on the thumbs is to use a Windows Mobile Pocket PC loaded with Phraze-It® software. Phraze-It enables users to type with their index fingers on large touch screen keys. Although the buttons are large, Phraze-It® leaves ample room on the screen for viewing and editing six or more lines of text.

Phraze-It® provides a choice of eight keyboard layouts for typing with your fingers and also for one-handed or two-handed text entry. The unique Phraze-It keyboard is based upon patented technology and will let you type with your fingers naturally. You can type emails and instant messages as well as reports, memos etc. into Pocket Word. The large touch screen buttons enable you to enter text comfortably, accurately and efficiently. With Phraze-It you do not need to tote a laptop and you can type very handily in the middle seat of an airplane.