those modern sink not very precise also, sometimes have to move
your hands about for sometime before the sensor picks up the
motion. if they install those, very soon you will see the baristas
shadow boxing the sensor instead of making coffee. 
They don't actually have to rely on proximity, it can just be a
mechanical switch with timer for the water run. The weight of the
spoon will open the tap, and the timer will cut it off,
simple.
