Tire monitors on towed or toad

I have the Tireminder system and it works fine on the toad tires. I am not sure what the issue is...

If someone developed an RV TPMS system that could also monitor toad factory installed monitors it would probably cost more than the expense of four more sensors for your toad! This is assuming that the car factory system is even 'wireless' and not some other technology.

Do you have any links to reports of OEM TPMS interfering with aftermarket TPMS? There are number of things that can temporarily interfere with either one, but I'm not aware of it being a significant issue among RV'ers. Each car company uses its own TPM setup, using differing frequencies and codes, sometimes even differing from model to model. Some do not even use individual tire sensors, instead using RPM variations detected by the ABS and other OBD input to identify a low tire. With all of that variation, making a monitor that's capable of working with all, or even most, of them, would be a major challenge.