Can This Model Be Hacked?
I guess it depends on how traffic bypasses the meter. It would be fairly foolproof if traffic bypasses the meter when a "premium" app uses a known set of network end points. However, if it's not tied to known end points and it's just the app identifying itself to the meter, how long will it be before hackers root the phone and send random "premium" app signatures, regardless of the app in use, to bypass the meter? Granted, it's a bit dangerous since they know who used the data but if you own the premium app, whose to say you just didn't use it a lot? Of course if they can track the end points it could be a dead giveaway when lots of traffic was exempted from sites the app wouldn't use.
The premium app could protect itself by passing on usage costs to consumers but then what's the point? That's like calling a free customer support 800 number and then getting a bill in the mail for the long distance charges. You might as well just pay AT&T unless the company heavily discounts it.