Heart Rate Monitor

I have a Polar F60 (I think that's the model). I LOVE IT. You have to wear a strap around your chest but when I workout, I just tuck it between my sportsbra and chest. The battery life is forever and you can easily adjust your settings as you lose weight. My favorite part is on Sunday's when it beeps at you to show you what your total calories burned that week are.

If you want to wear one all the time, I'm not sure you would like the chest strap but for workouts it is great.