Here you have an easy way to detect shakes on mobile devices with equipped accelerometer:

var lastShake:Number = 0;
var shakeWait:Number = 600;
 
var acc:Accelerometer = new Accelerometer();
acc.addEventListener(AccelerometerEvent.UPDATE, onAccUpdate);
 
function onAccUpdate(e:AccelerometerEvent):void
{
	if(getTimer() - lastShake > shakeWait && 
			(e.accelerationX >= 1.5 
			|| e.accelerationY >= 1.5 
			|| e.accelerationZ >= 1.5))
	{
		shakeIt();
		lastShake = getTimer();
	}
}
 
function shakeIt()
{
	trace("device has been shaked");
}

Enjoy!