I don't like using apps like Foursquare that let acquaintances know where I am. Cloak is an anti-Foursquare, and I'm eager to try it.
Cloak bills itself as the "antisocial network." Just sync it with Instagram and Foursquare so Cloak knows where your "friends" are, all the time.
Finally, let Cloak know which relatives/coworkers/"psycho hose beasts" you don't want to see. It'll then alert you when you're entering their vicinity. Or, if you're feeling reclusive, have it notify you when anybody you know is around. It's a fantastic way to dodge the dreaded "stop and chat."