It's so useful to keep an eyeon your battery level, the problem is that these apps often drain battery themselves. Which ones have you found to be the best and why? Personally I've just installed batteryminder. I quite like the feature which calculates how long you have left based on your average use. However I have noticed a battery plummet in the hour since it has been installed. I'll give it a day or two to see if it settles down.