I considered that, but the washer and dryer are stacked (limited space) so the vibrations of the washer would be picked up in a dryer vibration sensor.

Is that really a problem though? If you're washing another load at the same time as the dryer is running, wouldn't you generally want to wait until both are done anyways so you can swap the wash to the dryer after getting the dry load out?

Also at least in my experience the dryer takes longer to run than the washer, so if I've just rotated a previous load and started both at the same time I'm always waiting on the dryer to be able to do the next one.

Not always. I only put sheets and towels in the dryer, everything else gets hung up. So I may do two or even three washing loads in the time of a single dryer load (it can be very slow). So I'm much more interested in when the washer finishes than the dryer.

I tried that, and found dryers actually vibrate so little that most sensors have a hard time reliably detecting it.