Facebook Breakup Notifier http://snapvoip.blogspot.com/
"You like someone. They're in a relationship. Be the first to know when they're out of it." and at the same breath Breakup Notifier likes to promote that it has got nothing to do with stalking, by retweeting tweets like below.
In either case, the app which was thought about as a joke, has blossomed and attracted a couple of hundred thousand users within a day, and it must be more now.
As for the claims or denials of stalking, you be the judge, the developer Dan Loewenherz says;
"I just really hope people use it for good, not evil," he said. "It's really a practical thing. If you're going to refresh someone's page 20 times a day, why not have an alert on it?"Either way, I am sure he will be happy with the app, which is free for now will charge, like $5 for tracking 7 people, man that is stalking made easy!
The New York Daily News