If you want to share location data either publicly or with friends only, Google Latitude gives you some great controls on how you do that. I can create this badge as seen below that shows the public basic city information, while a small group of close friends can see a much closer look of where I am and I don't have to check in anywhere to make it happen. It is automatic as long as I review my cell phone map from time to time.
Where is Phil Yanov?
