In “California”:http://www.dfw.com/mld/dfw/news/9588858.htm?1c a man attached a cellphone to an ex-girlfriend’s car and used it to stalk her (The woman eventually caught the guy under her car attempting to change the cellphone’s battery). Of course it is much easier to simply track your target’s cellphone – something that is apparently being done more and more frequently in Korea. I think all services should require the tracked phone user to acknowledge each tracking attempt.
See “this item from my archive”:https://blog.org/archives/000712.html for info on UK cellphone tracking services.