Tg is a project mainly written in JAVASCRIPT and PHP, it's free.
Team: http://facebookgirlsintechdevgarage.pbworks.com/Find-friends-nearby-to-participate-in-activity-or-event
Mockups:
web: http://www.luckymethod.com/staging/togethr_html/ mobile: http://www.luckymethod.com/staging/togethr_android/