Anyone with an Android phone, and I think anyone with an iPhone that uses Google Maps, can go to Google Maps and look at their "Timeline." It shows where the phone occasionally pinged a location. So you can see on a day by day basis where you've been.
Yes maybe a little intrusive, but also kinda neat. I'm not doing anything sketchy so for now {wink wink} I don't care. I also know how to prevent it if I ever feel the need to do so. However, here's my plan:
The next nice day I'm going to go for a motorcycle ride. Before that, I'm going to spend some quality time on Google Maps planning out a route. When I, or more importantly if anyone else looks at where I've been, my route trace is going to form a closed fist with one particular finger raised... ;-)
It is my understanding that smart phones will ping cell towers even if tracking, etc., is turned off no matter what. This includes when the phone is off or powered down - as long as it has battery power it will ping and can be tracked.