I was reading on the AERC facebook page and someone was talking about wanting to use their phone for a 50 mile endurance ride but her phone's battery wouldn't last that long.
One rider posted she put her phone in Airplane Mode so her battery lasted longer. I was interested since I use my phone alot for my derby miles (it records more miles then my Garmin GPS). So I did a google search. http://en.wikipedia.org/wiki/Airplane_mode. I have a Droid Razr X and on my phone I found out that it does save your battery, but it turns off the ability to send or receive calls or texts. That's OK for me, I don't really want to send or get calls while I am riding. If you try to send a text or call it will ask if you want to switch it back. Saying yes will automatically switch it off and send your text or call. Since I like to ride lots of miles for many hours this is great news :-)
More great news is if you switch your phone to airplane mode, you can charge your battery faster. Almost the same as turning your phone off but easier.
Thought I would share a little info with my fellow derby riders. Gotta get all the derby miles we can :-)