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.