Sensors have accelerometers to detect motion to activate and transmit. Otherwise they go to sleep to save battery power.

 

I ran a set of tires/rims last winter without sensors, the take offs were in the garage next to the truck. When I would leave and travel approx. 10-15 minutes/15miles the fault light would come on in the truck.

When I would get home and park the truck in the garage the truck would pick up the sensors and the light would go off showing the tire pressure of the take offs.

5 months before I put the originals back on. So no, they didn't go to sleep.