I also suggest looking into "Battery Widget" by JH Jeong. It has an option to show the percentage in the notifications bar, and so is visible throughout most applications on the phone without needing to go back to the home screen.
Also tells you other info about your battery when you go into it, like temperature, how long it'll take to charge, rough estimation of how long it'll last discharging based on current use, voltage and a few other bits and bobs.