I have the Jawbone UP24. Right now, the red Jawbone UP24 is selling for about $69 on Amazon, and that's about $30 less that the blue or black ones.
The Jawbone app tracks steps, which motivates me to move more; gives me a reminder buzz to move, that I can set at the time interval that I desire; tracks my sleep not only telling how long, but also the quality of that sleep by telling me how many times I woke up during the night, and how much deep and light sleep I had (that helps me to consider how coffee and other habits might be affecting my sleep. I can also set my wrist band to emit a buzzing that will wake me in the morning. I does a few more things that I can't remember right now because I am not using them at the moment, but it also provides me daily bits of information on healthier living that I can choose to read in more detail if I want. The other important thing that it does is to allow me to link my stats with a friend that also uses the Jawbone UP (the UP24 links to your phone with bluetooth connect so it is always updating, while the Up version links by using a cable and only updates when connected to the phone). Having a friend's stats, and knowing they can see mine definitely makes me try harder on the days that I don't really feel like doing it.