Bizarrely this works.
My wife and I used this every day for about 6 months, vying with each other for most steps taken, and other minigames in the pack.
It becomes habit after a while to have the monitor on you at all times. I STILL have it on me now, although I check my steps weekly rather than daily.
The monitors have a light on them which flashes red if you have not reached the target you have set yourself, and green if you do. If it's red, you do feel like taking a quick walk to "get green".
Nice purchase. Even made me realise that one of the offices I work at gives me 2000 more steps a day without even trying!