In 2012, Christian Reß and Marvin Killig, the two master students from the Hasso Plattner Insitute, founded PlaytestCloud - a platform for crowdsourced iOS games playtesting.
PlaytestCloud is the fastest and easiest way for iOS-game-developers to have their games tested by real players during development. Therefore PlaytestCloud offers a platform, where developers can make their games available for testing. Testers are rewarded for the feedback they provide.
Link to PlaytestCloud
Interview with the founders on HPI Connect.