David Yanofsky:

Biking? Google probably knows you are. Up a mountain? It probably knows that, too.

The Alphabet subsidiary’s location-hungry tentacles are quietly lurking behind some of the most innovative features of its Android mobile operating system. Once those tentacles latch on, phones using Android begin silently transmitting data back to the servers of Google, including everything from GPS coordinates to nearby wifi networks, barometric pressure, and even a guess at the phone-holder’s current activity. Although the product behind those transmissions is opt-in, for Android users it can be hard to avoid and even harder to understand. Opting in is also required to use several of Android’s marquee features.