Cloak (iOS)

Physically avoid anyone you'd rather not run into.

Hey, this is the co-founder here. A solid 3 months late to this thread, but if someone stumbles upon it, I'm happy to answer questions.
Kinda love the negative POV on this app. You can flag someone so it alerts you if they are nearby and you want to scram. Requires Instagram or Foursquare authorization for the location data.
Ha, technology. Unfortunately since it's only using Foursquare and Instagram location data to track people, it won't be very accurate or real-time.