I have the cheap pretender, the Mi Fit, which costs around £30, and I love it. It seems accurate, and I've had it two years now without getting bored. It replaced my trusty old pedometer, which I also found to be a great incentive to get more exercise. I know I still don't do enough - 10,000 steps a day was just too much, so my target is down to 8,000 - but it does spur me on. I like the sleep monitor, and it has actually encouraged me to try to get to bed a bit earlier, as I invariably wake up too soon in the morning and have trouble getting 7 hours in. Mind you, it's not much use knowing that I don't get enough deep sleep without my being able to remedy it!