One adds autoplaylists (iTunes smart playlists) to Google Music: https://autoplaylists.simon.codes.
I'm working on my next, which provides business analytics for Google merchants: https://www.simonmweber.com/2017/03/18/google-payments-cente....
My SaaS adds autoreplies to Google Chat and Hangouts: https://gchat.simon.codes.
You can find the business details in https://www.simonmweber.com/2017/01/09/side-project-income-2....