1. }}foursquare. http://foursquare.com/. }}foursquare. http://foursquare.com/.
2. }}Google Latitude. http://www.google.com/latitude. }}Google Latitude. http://www.google.com/latitude.
3. }}Gowalla. http://gowalla.com/. }}Gowalla. http://gowalla.com/.
4. }}Helio. Available from: http://www.helio.com. }}Helio. Available from: http://www.helio.com.
5. }}Locaccino: A User-Controllable Location-Sharing Tool. http://www.locaccino.org/. }}Locaccino: A User-Controllable Location-Sharing Tool. http://www.locaccino.org/.