How about an app that tracks monthly bandwidth usage so that users have a better knowledge of where they are vis-a-vis the soft caps that some carriers put on their "unlimited" accounts?
(See I got billed $300 for data use - Are you a ROGERS User?
All it would need to do is let the user tell the app what the start date of their billing cycle is and then keep track of traffic to & from the handheld.. I'm not an application developer (or a programmer..), so I'm not sure of how difficult this would be... but I would think accuracy within a few megs would be very helpful to have.
Feel free to PM or email me if you are developing or want to develop an app like this and want beta testers/feedback/etc.