One really-cool way to solve that problem is to embed a 7-segment LED under each keycap. You walk up to the keypad and the 0-9 digits appear in random order. No one can shoulder-surf, look for wear or IR emission from the buttons, or train on the click sounds.

Dell had those on every lab door in the building back in the early 90s. You felt like 007 every time you punched in your access code. I've never seen them anywhere since.

And now days I can't put in my card's pin without 10 overhead cameras aimed at the register area. All the cameras of which are network-connected, video stored persistently, and high res/fidelity enough to here the little beeps as I press the keys, and to know that I've hit the enter because the screen indicates it immediately. But then Dell cared about its own security, and the grocery store doesn't give a single shit about whether my life is ruined by identity theft.