Me and my friend built a small app that makes it easy to share your door codes with each other. So now you never need to remember or ask again. The best part is that the door code magically pops up when you are close to your friend, even if the app is closed. And security wise, the codes are encrypted on your phone locally and not in a database. We moved fast, in fact the app was designed, developed and in App Store 3 weeks after we came up with the idea. Test it out here.