Schrader valve mounted TPMS's have proven to be the wrong approach.
They are commonly destroyed when demounting tires
. The stems are exposed to the elements and can not be serviced separately. A bad two cent core could result in spending hundreds of dollars for replacement.
This is something to be considered when choosing a new tow vehicle...
Some companies,such as Ford, use an internal rim mounted TPMS. It is out of harm's way to a tire tech with a minute's training, and they allow for changing stems when purchasing new tires
. They can also be moved to virtually any aftermarket rim.
They still don't allow for battery
change and like the schrader mounts, must be replaced as a unit.
Remember these things and their costs are mandated on cars after 2007... pushing a few more people out of the market for a new car.