But if these cars can be "commandeered", they (i.e. my movements) could also easily be tracked by the companies themselves (with the information then sold to "trusted partners"). For some reason, that frightens me more.
COTRAVELER[1] is much easier and costs almost nothing. Just having a cellphone in a car (either in the driver's pocket or "OnStar") - which only needs to be on and giving presence notifications to the local tower - is enough to get very accurate near-realtime tracking information. The only costs are read-only access to the tower logs and a few SQL JOINs.
[1] https://www.washingtonpost.com/apps/g/page/world/how-the-nsa...