1. What's the estimated bandwidth impact of this data collection? Many users have very limited data use, and chatty messages on play/pause/volume change wouldn't be appreciated.
2. HTTP or HTTPS?
3. How does it work with other apps (like Google Music) that might provide more music details? Like does it send more information when the id3 tags have all the fields filled in? Things like comments, encoding, etc might also be transmitted. Streaming services like Spotify probably try to trim that as much as possible, but local files could have a lot more data.
4. Can you see anything about the anonymous id that might make it not that anonymous? I mean, the device serial number alone kind of defeats an anonymous id. But there's been a fair amount of work in reidentification of anonymous data, and many developers take shortcuts when generating their "anonymous" data. (https://arstechnica.com/tech-policy/2009/09/your-secrets-liv...).
5. It's sending this data in the background, correct?
6. What does it send (if anything) during calls, emails, texts, map navigation, and voice commands?