The Cloak app is an app that allows you to be incognito. It uses the location data from your Foursquare and Instagram account to know exactly where all your friends are so you don't have to worry about running into someone you are trying to avoid.
The app is like a reverse of Foursquare. Instead of being able to find your friends and meet up with them, you can now see where they are to avoid them. We all have those days when we want to run some errands and we don't want to run into anyone we know, but sometimes that can be difficult. The Cloak app helps you avoid running into those specific people that you want to steer clear of, at least if they are actively on social media accounts.
The app was made by Chris Baker who has also made other prankish sites and apps.