If you ever download or upload a picture in the app, you’ve likely granted full access to your photo library, which includes location information on every photo along with timestamps.

Also just direct location access, even when it’s running in the background.

What orientation the phone is in (are you laying in bed?) and is it moving?

Then of course more specific metrics within the platform around how long you looked at a post, how fast do you scroll here, how much do you read certain comments compared to others, etc. Those platform metrics are a lot easier to track when you have full hardware access instead of just the apis that mobile javascript provides