While I don't work too much in it due to the current lack of time, I built cryptocoinalerts.net (
https://github.com/AlexITC/crypto-coin-alerts) some months ago, decided to be an open source project from the beginning and while it has served its purpose (put real work in a project that potential clients could evaluate), I ended up extracting a library from it (
https://github.com/AlexITC/playsonify) which I have being used in other projects.