I have a Jawbone UP 24 and I really like it. Lightweight, doesn't make me sweat under it and it reminds me when I need to get up and move.
But the really interesting part is the sleep analysis. All my working life, I got by with five or so hours of sleep during the week and then I would sleep ten hours on the weekend. Since I've retired, I find it fairly easy (most of the time) to sleep a full eight hours. Lately I seem to be fighting some nights of insomnia...no, the band doesn't help but it does let me add nap time.
"Insomnia - when writers work." ~ DB McNicol
Another feature I recently found in the app is the ability to add in other exercise like swimming, hiking, tennis, basketball (and more), but more importantly to me is being able to add yoga. I can add my classes at a moderate level and my at home yoga at an easy level. They seem to have thought of everything!