I have an Apple Wireless Keyboard and a Magic Trackpad, and I was wondering if there is a way to monitor the battery life remaining/percentage like there is in OSX.
There isn't a GUI for read wireless mouse or keyboard battery data.
You can find useful information on sysfs under
/sys/class/power_supply/. For example the Apple Wireless Keyboard is under
/sys/class/power_supply/hid-78:CA:39:4E:6F:C7-battery/. In the device directory there is a file named
capacity, this is a capacity in percents.
So in summary, for reading Apple Wireless Keyboard battery capacity you should do:
hid-78:CA:39:4E:6F:C7-battery can be different for your device.
According to this article on webupd8, this functionality is planned for Ubuntu 11.10 as part of Ubuntu's new Power Indicator.