Requires iOS 5 or higher:
Have you ever wanted an app like coconutBattery for iPhone?
Well, this is a tweak which does the same job.
BatteryInfo shows all your important battery information in the notification center!
+) Battery state
+) Battery charge
+) Battery capacity (design capacity and current capacity!) –> battery health
+) Battery loadcycles
+) Battery temperature
iOS 5+ required!
Tested on iPhone 4 only, but should also work fine on all other devices.
NotificationCenter addons can be configured from the Settings app, in the Notifications panel.