James Jerlecki can’t tell me exactly how his new app is going to be useful, but he thinks teens are gonna love it. This kind of space — which is anonymous, yet personal — doesn’t really exist outside Alcoholics Anonymous. So Jerlecki built Rumr, an app for iPhone and Android that lets you carry out anonymous group chats with friends. In other words, you’ll know which ten friends are in your chat, but you won’t know who’s saying what.