i bought three of these for xmas and all recipients thought they were great (8,18,24). They are very small (fit in a pocket/bag easily)and light and feel a bit tacky, but believe me they work a treat, well worth the money I paid for them.
Got this at Christmas for all the family (16 & 18 year olds) and we have all had a brilliant time on it. We all had a great laugh but it gets very competitive, even found myself sneeking off for a go to increase my scores. Not sure that I could follow a fitness regime in this way though, I see it more as a game.