Is there such a program that would allow you to use your Droid X as a Heart Rate Monitor to use when exercising?
Not without being clumsy. You have to hold your finger over the camera to get the app to work. So, using it while exercising isn't really a great solution.
It would be cool to have some kind of USB or BT accessory that did the monitoring.
But I havent seen anything like that.
The heat rate App(s) that are in the market all work great. (it isn't a hard function to program)
Good luck.