Aydan,

Not entirely correct - it is technically quiet possibly to control a helicopter without a "flight control system". People have been doing it with real radio control choppers for a long time now.

That said however this is a fake video still. To control a chopper you need to control the following 4 axis:

1.cyclic Pitch (nose up and down)
2. cyclic Roll (lean left and right)
3. Yaw (rotating on axis)
5. Collective or if you will the z axis

I am sure the way this guys in controlling his chopper with his N900 is probably possible since the N900 can sense all the of these movements.

The real crux is that anyone who has ever flown a real or model helicopter will know that if you give right or left cyclic you always need to compensate with more collective or the chopper starts to drop down. Clearly in this video the guy makes the chopper roll to the left with a tilt of his N900 only and no added collective like he does further on to get it to go up!