The Telegram Python Library by Anton Grigoryev is a Python library for developers to use with the Telegram API. The goal is for developers to be able to implement MTProto protocol Telegram API on Python. The Telegram API allows developers to access and integrate the functionality of Telegram with other applications.
Food-sharing mobile photo app Foodspotting had an API since day one. Of course, every mobile app has an API, at least if it needs to store or retrieve non-trivial data. Most of those interfaces stay hidden away, private APIs with only that single, internal audience. Foodspotting, on the other hand, signed Zagat as an early partner and now also has OpenTable, among others, using its Foodspotting API. The company is not exactly making it widely available for any developer, though the documentation is public, planting it in a vast grey area that's becoming increasingly common.
Google Cloud Vision API gives developers access to powerful image processing and analysis tools for use in any project. This tutorial on Google Cloud Platform shows followers how to use the API to detect faces in an image, and use the returned coordinates to draw a polygon around each face.