[asher_]

Based on the demo they showed, this isn't needed. As long as they know the orientation of the device relative to a flat plane they can move the virtual items within the bounds of that device's screen. When it crosses over on to another device, it only needs to calculate movement based on it's relative orientation.

[timgrossmann]

Yes, exactly. If it enters the space of a tilted device, a force (depending on the rotation of the device) is applied to ball.