Cell Phone Carriers should give you tools to manage your minutes

For instance, text you warnings if you are exceeding "run rates". For instance, if you are 1/4 of the way through the billing cycle, and have used >= 1/4 of your total minutes, that would merit a warning. They could be configurable, to avoid annoying people who know what they are doing. Of course this goes against the company's own interests, to an extent, so is not something they have invested in. Another idea for an iPhone/Android app (but tough, because requires account data that could be hard for such an app to access, without the carrier's blessing).