You can track anyone that has their cell phone on them, and have been able to for years. There are even public tools from public companies that do that. You can tie this to other logins, e.g.
See here: https://maps.google.com/locationhistory/b/0?hl=pt-BR
Change that map to 7 days, and hit play. I know it’s in Portugeues or whatever, but check that.
Or enter your twitter handle with the @ into google maps, etc.
You can change the language to English in the lower right. Where do I put in the cell phone number I want to track?