It seems to me that if an attacker can get access to your microphone and camera, you have way bigger problems and they don't need your PIN at all.
<i>Getting rid of passwords altogether and using fingerprints or face recognition are offered as more drastic solutions.</i><p>Despite all the recent hoo-ha of how the iPhone 5S took mere days to circumvent the fingerprint reader using some latex and glue.
So, the next step is to use the camera and microphone on your phone to detect the PIN on the phone that somebody standing next to you uses. With a directional microphone, a good video camera and some smart gonio to reconstruct eye position relative to the screen it should be possible to detect the PIN even if the screen isn't visible in the shot.
I wonder how this would compensate for arbitrary movement of the phone. You could choose a pattern, or randomly tilt the phone as you press/slide.<p>I'm pretty sure that if you're hurried and forget, the software could easily deduce the pin.