FireFly is the new Location based Check-in service that is based on Twitter Places API and uses the twitter social graph as your friends. The iPhone app design is very similar to foursquare or gowalla, you can check where your twitter friends are checked-in, you can browse nearby places and check-in, and also attach pictures with check-in. It is not clear if the it just shows friend check-ins done using this app or does it also pull tweets with location tag from twitter.com, it does not look like it pulls location tagged tweets of friends. Foursquare and Gowalla tag check-ins with twitter places, it will be cool if Firefly can pull tweets with location tag into this service, then it will have aggregated stream of check-ins for twitter social graph. Overall it is a well designed app, but the big question is, is it just filling a hole that twitter can implement on their own?