Yes, motion detectors are useless...
If the detectors are relatively high, you can use shields to block the floor, however if there's anything cats like to do is climb, that will still set them off
For animals, magnetic switches on doors and windows as well as glass break detectors are required.
Personally, my iRobot Rooomba, automatic Vacuum cleaner does not set off the motion sensor.
I have him "Fred" run every other day, and have had no problems.
But then, he's only 3 to 4 inches off ground.
My Dobbie, will set off the sensor.
So you have 2 exremes, from the small vacuum, to the larger dog.