I'm looking for recommendations for a droid that I can use without service - obviously I will be buying used. I am planning on using it for its wifi and gps mainly. I am an outdoor and fitness enthusiast so the apps I'd use would be things for tracking my bike rides, using it as a heart rate monitor, etc - plus general web surfing via wifi. Assuming all this is possible without activating it with a carrier - which droid would be best suited for this? Cost is a factor, so I am not looking for one of the newer phones, since I would like to keep my cost to 100 or less. Thanks!