I have, and I wouldn't recommend it either. iDevices don't have enough computing power behind them to do anything useful. My friend's iPad 2 maxed out at 12 h/s. To put this into perspective, my old computer reaches between 4.5-5 kh/s (400x more powerful), and that's 12 years old btw. So there's no real point in it at all, it's just a waste of power as Layerz said.