Detect BPM/tempo in real-time

[barbeau]

Is your feature request related to a problem? Please describe.
It may be useful to collect avg song tempo in real-time so we can label the song for further group analysis.

Describe the solution you'd like
Looks like existing libraries might be able to help with this:
https://github.com/widget-/bpm-detect

Describe alternatives you've considered
Do analysis server side, although that means we need to find the exact song being listened to on the device.