The Chartboost iOS Sample Code by Chartboost demonstrates how to integrate charts into game monetization applications. It includes an SDK with Chartboost initialization, rewarding video ad, and integration testing.
For those who get their kicks out of a good old physical board game, BoardGameGeek is a fun application that may be of interest. It's an online board gaming resource and community that is constantly updated in real-time by it's growing list of users. Users from across the world can participate in reviews, ratings and live discussion forums, add images, find play-aids, access session reports and more. BoardGameGeek also provides the BoardGameGeek API which means this functionality can be easily accessed and integrated with other applications.
iOS 10.3 introduced new app review tools for developers in the form of the Reviews API. The goal is to allow developers to ask for feedback in a less intrusive way while also giving them the opportunity to respond publicly. The end result should be a win-win for developers and app users alike.