BatteryDoctorPro - Recently I've noticed that my iPhone's battery life has been getting worse. At first I thought that maybe one or more of the tweaks I had running was causing it, but after uninstalling most of them, leaving just the basics behind, the problem hadn't resolved itself.
BatteryDoctorPro is a tweak that is designed to improve your battery's performance both through toggling your setting according to your current location (home, outside, etc.) as well as inactive time, and even by using clever charging techniques to improve the health of the battery itself!
After using this for a week or two, I am VERY impressed, my battery life has definitely improved, and I have found that the life expectancy that the tweak provides is extremely accurate!
Even though this app has "Pro" in the name, don't be put off, it is free and easy to use, so definitely give it a try!