Enter BatteryEx. It places an icon on your homescreen displaying your battery level. You can also optionally display the voltage and temperature. Another feature is that you can add a small icon at the top of the homescreen displaying the battery level.
It seems pretty accurate and could be useful when you're low on juice to monitor your levels.
In the paid version, there is a 'Booster' feature. I'm not exactly sure what this does, but it sounds pretty obvious.
Get it here:
Sent from my BlackBerry 8900 Javelin.