You screw them on your valve-stem & the device gives you the air pressure of each tire. If you rotate tires, you just move the pressure reading caps to the correct wheel. They are marked for each tire location. This is so simple!
A 5-year old could install this system on any car!
When a factory sensor dies, you have to buy a new sensor and pay a tire shop to install it. What a pain! If you don't clone the sensor, you may have to pay someone to have your car reprogrammed.
These outside units have watch batteries in them. When the battery dies, you can just change them yourself. For $40-50, you have a system that will give you the psi of all four tires. You don't have to pay anyone to install a sensor or pay a dealer to reprogram your car's TPMS. We talking about $40-50, screw them on your valve-stem, & you are done. Some use the 12V outlet to give the psi reading, some use a solar panel unit, & some come with both options.
Just an option some may want to consider. You could use this along with your existing TPMS, because it's a stand alone TPMS.
If you need a visual of how this all works, good ole Scotty has one below.
The point is a child could do this. It's cheap ($40-50) & it involves zero tools that you need purchase! This could be added to any car from any time period.