Consume

Devour as much as possible of your phone and internet plan, with the best usage monitor around. Consume covers a wide range of service providers. It can even monitor several accounts at once, letting you keep a close eye on your mobile phone calls, data and home internet, right from your iPhone. Awesome.

Please note that most mobile phone carriers require that you register for online services before you can monitor your usage using a web browser or Consume (more info).