It could really great thing if you can see the remaining iphone battery in percentage in the iphone status bar, as apple as finally rolled out some changes in the firmware 3.0 and other firmware released after words. With this small hack you would be able to see the exact battery percentage in your iphone status bar.
For iPhone 3GS
Locate Settings on your iphone home screen or it could be on any other screen – you can search for settings through the search screen
Under settings navigate to Settings >> Usage – here you will see the Battery Percentage switch and toggle it to ON and you will instantly see the remaining battery percentage in your iphone status bar
For iPhone 3G and 2G [ Jailbreaked ]
In case of iphone 2G and 3G you cant see the option shown as default under settings, as the above option applies for iphone 3GS only. In order to see the remaining battery percentage in iphone status bar you will need to install SBsettings or Battery Control under cydia repository. In order to install SBSettings you will need to go to search in cydia and type the these applications names.
Under SBSettings you will slide the SBSettings Menu Bar by sliding your finger across the iphone status bar, and press More
Now select Extras & Options
Now Select Numeric Battery and toggle it to ON
If you have installed Battery Control then Go to Settings >> Battery Control
Now Select Show Percentage and toggle it to ON
Found In: Cydia Cost: Free