The people at google or apple. Perhaps your phone manufacturer if you don't use a first party phone. The cell phone companies (approximately but they can triangulate pretty well). Potentially any retail establishment[1]. As facial recognition technology becomes more mature it won't even require a phone.

[1] This one is a little uncertain because it relies on tracking bluetooth / wifi radios and you have to do a pretty complex setup. Simply establishing presence is harder (and ofc the whole thing can be blocked by secure operating systems).