You can attach some photodiodes to your screen to control things. And use the camera/mic for input.

Now that's a funny idea. But it's true!

	▲	amelius an hour ago \| parent [-]
		I think you can attach a keyboard to a phone over USB, and in theory it can provide both input and output (you can control the LEDs from the host computer). That would be a more convenient route, I suppose.