We are actually building a similar system and the feature you are talking about will be included in a little bit different way. Our system called Inging will be web only at first. We should be ready to release a beta in a month. Inging is an Interest Based Social Network connecting you with others purely based on your favorite activities! The URI is http://www.inging.io . Right now we are allowing people to sign up to get the first invites as soon as we release the beta.