First let me tell you my experiences with TST. They are a fantastic company to do business with. I have the 507 system for my rig and toad and love it. I had the 510 system before and when the batteries started to go around the 4-5 year mark I upgraded to the 507 with the flow through sensors.
Now to your question, the toad internal monitoring system has nothing to do with you adding on a sensor. Your toad's system will still work when you are driving it as it normally does. All you are doing is screwing a sensor onto the valve stem. The car's system is internal and has no effect on the screw on sensor. Best wishes as you start your RVing adventure.
Many happy miles and smiles.
Dan 2008 Allegro 32 BA FRED, Honda Fit
There are 10 types of people in this world. Those who know binary, and those who don't.