Just picked one of these up for my sister for an Xmas present. Was about to pay £25.00 yesterday, but it has dropped another £5 overnight which is a nice bonus.
Dont forget quidco to add a few pence more off that price.
Reading about the product it appears they have updated the firmware to fix most of the major bugs and the watch strap is now updated to remove the issue that would cause the unit to learn to fly. Also now compatible with standard watch straps if the sports design isn't to your liking.
Works with most Android phones - If you run Android 2.0 or greater then it should work provided your phone has bluetooth - However a compatibility list of confirmed working phones is listed in my post below.