ive used BUDDY RUNNER app. works good. tracks distance, pace, time, calories, maps route using GPS. Droid fits in most iPhone arm band cases. it is a bit heavy, tends to slide down my arm a little.. but doable.
iPod haters look away>>>> in all honesty, if you have an ipod nano or touch, the nike+ sensor is a much better way to go. the online nike running site is really awesome, can have an online coach, take part in challenges, much more user interactive, and fun!