Battery life on the iPhone is a big concern. Many like myself avoid using too many apps and manually keep toggling the data services on and off (also bluetooth / wifi radio), just to save some battery juice. Now that the iPhone doubles up as an iPod and a handheld gaming device the challenge to preserve battery is much more. Infact the iPhone 4 even brings in FaceTime video calling which adds to the load. So here is an innovative Cydia app by Bigboss that costs $5.99 but lets you make optimum us of 3G network.
Auto 3G simply turns off 3G (and falls back to 2G) when the phone is locked and enables it again as soon as you unlock the phone. Since the phone lies idle in locked mode for most part of our day this can save a lot of energy by switching off 3G when unnecessary. This hack alone can get you upto 100% extra battery life!
The price tag of $5.99 for this app, you decide if its worth it!
Search ‘Auto3G’ on Cydia. (Requires a jailbreaked iPhone)