Your alerts are an awesome feature. Maybe you can improve it. When you're setting up a new alert, you're provided with the three options (Minutes, Messages, Megabytes)
If I'd like to have an alert for when my balance is getting to expensive, I need to do some research and math. First I'd need to look up the prices for each bucket and estimate the numbers to input for an alert where I think its getting to expensive.
A simple solution would be to add a total bill amount option to the new alerts.