On clicking I find:

Tone Analyzer (IBM Watson Developer Cloud)

The Tone Analyzer service uses linguistic analysis to detect emotional tones, social propensities, and writing styles in written communication. Then it offers suggestions to help the writer improve their intended language tones.

It detects three types of tones, including emotions (negative emotions, cheerfulness, anger), social propensities (open, agreeable, and conscientious), and writing styles (analytical, confident and tentative) from people’s writings.

I.e. it's a hosted sentiment-analysis engine.

Most existing sentiment-analysis engines have quite poor accuracy, so it could be useful to have another entrant. I might try this out.