What can i do for the -3degree problem with motion sensor?

not sure, likely they can just apply a software update once they figured out the batch of affected phones. Maybe they'll add a software patch that'll let you recalibrate the default. It seems consistent from all the reports I've seen, including my own 5S, off by about 3 degrees only in the horizontal position, so it seems like a manufacturing defect or calibration step.

Apple, I'm sure, is working on it. If it's easy to fix with software, it will be out shortly with software update 7.0.3. Just sit tight.

If it's a hardware problem, it's unlikely Apple will be able to fix it, and they're equally unlikely to take back millions of phones. My guess is we'll get a free case out of it -- just like with "Antenna Gate".

My data:

My iPhone 4 running iOS 7.0.2 agrees with reality (defined by both my bubble and digital contractor levels).

My 32GB silver iPhone 5s is off by 3 degrees (level function) and about 7 degrees (compass function). I haven't run into any buildings with Tom Tom yet.