The Pocket Boom provided by MobileFun (who do some of the best iPhone accessories) is a brilliantly versatile and pretty unique portable speaker. The Pocket Boom is a small cylindrical object that'll fit in anyone's pocket, making it very portable. Popping off the top of the Pocket Boom reveals a sticky pad with which you stick the device on to pretty much anything. Insert 2 AAA batteries and connect any 3.5mm audio device (Phones, iPods, etc) and suddenly you'll find the sound of a speaker a lot bigger than the Pocket Boom suggest resonating from the object you stuck it to.
The sound quality, volume and bass all depends on what you decide to attach the Pocket Boom to, hollow metal objects worked very nicely, along with wood working well also. We found that metal gave a much louder sound whereas wood gave a quieter but warmer and bassier sound. Glass doesn't work at all well however almost everything other than it gave good results.
The small form factor, unique idea and ease of use make the Pocket Boom a really good alternative to a conventional portable speaker. At £19.99 it isn't the cheapest portable music device around but just the unique way in which it delivers the sound makes it worth more, surely? Maybe it's just me being a geek that makes me love it, but even so, it would make a good gift for any geek!