Just did a similar HTML5 project last weekend. http://radiocollar.herokuapp.com / https://github.com/rickcarlino/radiocollar
This really is an area that has been neglected by developers. The main gripe that I have is that all of the geolocators out there want to force me to download an app, sign up, set privacy settings, force my friends to sign up, spam my facebook friends, etc. It's all just too much for a simple service like location sharing.