I have a Garmin Edge 520 and use the ANT speed sensor on the rear wheel, and a cadence sensor on the crank arm.
It works fine for measuring/displaying speed and distance while riding on indoor rollers and stationary trainer.

I think that's the only purpose of the wheel sensor, right? It works outside too if I forget to turn the GPS back on, but I assume when I have GPS on, the head unit is using that to measure speed/distance and not the rear wheel. Hmm...