[saguppa]

There's also this API by Microsoft Research. https://www.projectoxford.ai/

[coleca]

I will throw ours into the ring as well.

If you need to understand emotional reaction on video sources, our API can fill in the gaps not currently filled by Google's Cloud Vision API: https://www.kairos.com/emotion-analysis-api

Disclosure: I'm CTO of Kairos.com