iRate : App Rater Library
Many apps implement a prompt that ask or remind the user to rate the app in the respective app store. This, implemented correctly, usually converts well and results in an increase in feedback/rating for the app.
iRate lets you implement such a prompt easily for your iPhone or Mac App Store app. It prompts the user of the app to rate the application after using it for a certain number of days. It has automatic support for iOS fast application switching. Since it prompts the user only after a certain duration of using the app (usually a few days), only users who have been finding the app useful or using it for some time will get prompted and hence it will have a better conversion ratio. Detailed information on features and usage is available on the Github page and the repo also includes example projects.