This made me install an Android app (Seismograph) to test to see how my Nexus 4 picked up my key presses. I had it set to the maximum sample rate, with my phone

This made me install an Android app (Seismograph) to test to see how my Nexus 4 picked up my key presses. I had it set to the maximum sample rate, with my phone on the desk as close to my laptop as possible whilst not touching it, and it couldn't pick up anything. I suspect therefore this is more of an issue for to-the-desk peripheral keyboards. It does make me wonder though if the sound of each individual key press is subtle and unique enough to be identified.