"A new feature being discussed by the music service Spotify could use sensor's on the listener's body or in their smartphone to measure their heart rate and then use that to select appropriate music.

The more data Spotify can collect on listener habits, the better the recommendations its algorithms can produce. As well as music, motion, heart rate, and temperature, Spotify could start to monitor sleep patterns, according to Donovan Sung , Spotify’s product manager for discovery and recommendations."

Just like "Her".

This makes me want Spotify less, not more. I'll stick to Pandora.

Hopefully you could turn that feature on or off; which would make sense, or they would limit how many people would use their product.  In fact that's a pretty smart design choice for all features of products: let the individual choose what features of your product they would like to use, and you will win the market.

Yes, although 99 percent of users just leave on the defaults.