BattCursor shows the battery charge in percent directly under the mouse cursor not only this it offers many other battery-saving features like dim down the display brightness for inactivity, automatically disable the Windows Sidebar and Aero Glass when battery level goes down beyond a specific level.
The best feature of this free battery monitoring application is it always displays the remaining battery percentage under the mouse cursor which is seen all the time to the user, this could be really useful when you working on some thing important and your laptop is running out of low battery.
The basic requirement of this application would be a laptop with any version of vista installed and .Net Framework 2.0 installed. You can explore this utility to customize the various types of alerts related to battery.
You can disable aero glass and/or vista sidebar if the battery level is lower than specific percentage.