I created them to help me fetch information from each of these services, to integrate into a website to display more interesting and dynamic information to the viewers. I hope that they will help others do the same.
You can find the them in my Github repositories, and below, each is a file you could use in the /mu-plugins/ folder or include in a theme/plugin:
Each is fully working and the README.md files contain instructions, lists the available endpoints and gives examples code. None yet cover all available endpoints, just the most commonly useful. I will be expanding the endpoints available, documentation and examples over time.
I have stuck to the WordPress way of doing things on the whole and maintained compatibility with the WordPress requirements (e.g. PHP 5.2). If you have any problems or suggestions I would love to hear them on here or via Github issues.