If I had the ability to track users heart rates in response to advertisements, media, political content, etc that would be quite valuable for producing content that better captured users and made them feel what I wanted them to feel. Heart rate says a lot about what we're feeling and our attention, especially if you have it all the time and can match it to what we're looking at.
I mean, obviously. That's not the question though, the question is utility. There is undoubtedly utility, it's just that you are the product, not the beneficiary.
