I'm not brave enough to mount my iPhone 4 anywhere that it might possibly get hurt, but I have been putting it in my saddle bag for tracking my mileage and mapping my route. I use a $4.99 app called Cyclemeter. It works perfectly for what I want - detailed map of my route, log of the speed, and tracking my progress over time. I've had no problems with it working inside my bag. My commute is about 1 hour long and when I have the app running it burns through about 10-12% of my battery. Of course, if you wanted it mounted somewhere that you could see the display and had the screen on, it would probably eat up quite a bit more battery.