There is a software called Power Center:
Power Center is a battery management program that estimates the amount of time your battery has left to run, rather than the percentage of power left in the battery. It recalibrates its estimate each time and keeps a record of it so future estimates are more accurate. With the help of the Control Center, you can set the Power Center to inform you whenever the battery is lower than a specific percentage, at a specific percentage, or when the AC power goes on or off. In this version the window mode restoration problem has been solved. Version 2.12 includes a few minor bug fixes.
And here some nice battery test program (not really related, but just in case you'll need it):
Laptop Battery Tester:
This program can scan battery voltage, export them and show graph. Export data to MicrosoftExcel, or Picture export. Program can load old picture for compare results, changes and defect. Installer and uninstaller is included.