At first glance, you might notice that Habitshare sports an aging UI. However, don't let that take away focus from the app's core value proposition.
Habitshare is trying to make habit tracking social. The app lets you do that by sharing your habits with friends, who can then see your progress with your habits and stay updated.
The core assumption of the is that by sharing your goals and progress with habits with your friends, you increase accountability and therefore increase your chances of success.
Habitshare is a completely free app.