The Tire Pressure Monitoring System (TPMS) valve is a sender unit that is integrated into the valve stem. From the outside it looks like an ordinary valve stem. You can't see it from the outside since the bulk of the unit is located inside the wheel. Search on eBay under "Scion TPMS sensor" to see what they look like.
It should be a simple matter to move the stock TPMS units off of the steelies and onto the Ford rims. Along the way you will likely be charged to rebuild the sensors, like I was when I had my local wheel shop move my stock TPMS sensors to my alloy rims. My car was only 1 week old and had only 160 miles, yet the wheel shop insisted they had to rebuild the sensors. I think it was $4 or $8 per sensor.
