You can grep the battery level. The easiest way I think to do it is to install a system monitor. All kinds of them exist and I'm sure atleast one of them is your repository. Here's a list of tools that will give you constant read out:
Conky
Torsmo
aDesklets
gDesklets
SuperKaramba
I personally use conky, its lightweight, looks great, and tells you everything you need. Here is
my screenshot of conky, though its before I configured it to read my battery.
