A foot might be pushing it slightly.
But you know what I’d do if I were you? I’d get a bunch of SureFlap RFID cat flaps, remove the flap itself, unsolder the latch coil and connect a relay instead, and voila: you have yourself a very effective, el-cheapo cat detector that you can interface with whatever the hell you want. For 60 quid, you got yourself a nice cat-sized “detector tunnel” with a battery holder (the batteries last forever, even with hyperactive cats), the circuitry to read FDX-B and EM41xx chips that truly never misses a read, and an easily hacked interface. Strategically place the hacked catflaps where your cats have to go through them and you’ll be able to track their movements.
I know because I hacked three of those things to do almost what you want to do: I had two of them one after the other - as an “extended tunnel” - to detect my cats going in or out and prevent them from getting in with dead critters at night, and the other was used to release food into their bowls when I was away on vacation - all that controlled by my home server under Linux.