I am shocked that no one has attempted to make the “Forbid” app from season 2 of HBO's Girls. It’s incredibly simple: you select your ex boyfriend or girlfriend’s phone number and you are charged a penalty every time you text or call it. Genius!
It’s probably not possible to make this app on iOS (unless it’s a jailbroken phone with extra api calls), but I think it’s doable on Android.
Here is a video clip from the show explaining Charlie’s app in very fast dialogue: