UTCS doctorial student, Eric Rozner, has developed software that extends cell phone battery life by changing the way your phone interacts with Wi-Fi routers. His application NAPman--which is not yet commercially available--helps cell phones sleep more often. It also makes it easier and more efficient to use Wi-Fi signals rather than 3G celluar network connections when downloading data.
CNNTech report: http://www.cnn.com/2010/TECH/innovation/06/24/mobile.phone.battery.life/index.html
NAPman research: http://userweb.cs.utexas.edu/~erozner/papers/mobi092-rozner.pdf