[marcosscriven]

I wondered about doing something like this a while back - and it was the very quick cumulative error from double integration of acceleration data that stopped me from even trying. Clever idea getting the user to place the phone on the walls - as you say that would correct a lot of the errors. But also, as you say, unconventional room layouts get you back to square one so to speak.

[digikata]

I haven't played around with the latest generation of sensors, but if the time/distance error growth is small enough, maybe you can get model corrections down to the nearest 45 deg. If you can hit that threshold, you might end up fairly functional with possibly the next largest segment of non-rectangular rooms.