Anyone without an unlimited data plan knows about the struggle of working inside a carrier's tiny cap allotments. While plenty of App Store apps exist that can help you track data usage, a new jailbreak tweak called Membrane by iOS developer candoizo can take things even further.
Membrane integrates directly with the Cellular preference pane in the Settings app to give you fine-grained control over what apps connect to the internet over a cellular connection, and which ones don’t. It also provides real-time information to keep you alert about how you're using all of your data.