I tried to implement http://code.google.com/p/php-mobile-detect/ , and PHP threw some fatal errors.

So I'm using $_SERVER['HTTP_USER_AGENT'] , just to see what kind of results I collect.

In the first half-hour, one or more of my 4 sites has been visited by bots from google, bing , ahrefs.com , baidu.com , and ezooms.bot .

Devices have included "computer", Macintosh, WindowsNT, Sony Tablet... not counting me with my iPad and iPhone.

The number of bots really brings home the point regarding the claim last year that 50% of Internet traffic is not human!