3G Watchdog is not available for iPhone but there are a few alternatives with similar functionality. The best iPhone alternative is My Data Manager, which is free. If that doesn't suit you, our users have ranked more than 10 alternatives to 3G Watchdog and three of them are available for iPhone so hopefully you can find a suitable replacement. Other interesting iPhone alternatives to 3G Watchdog are 4Glob (Paid) and Omnistat (Paid).
4Glob is an application designed to track mobile internet usage. The application is designed for users who actively use mobile internet on their iPhone and iPad devices and are concerned about their communications costs.