The sensors.
Jeep
Motor home front.
Rears
When you drive away, in toad or coach, with out the other vehicle it takes about 20 mins before it starts beeping for lost signal. You can watch the pressure and temp change on the tires of which ever vehicle you in, the other sensors read outs do not change till it realizes their no longer there. If you shut the unit off then restart it, it will only give readouts upon the sensors it detects. No more beeping.
If you slowly unscrew on of the sensors, to simulate a leak, it picks up the sudden pressure change quickly and the alarm sounds.
Overall I'm happy with my choice.