No. That would be the geolocation API https://developer.mozilla.org/en/docs/WebAPI/Using_geolocati...

You can of course use that in conjunction with realtime web technologies: For example, see: http://leggetter.github.io/100-lines-or-less-js/realtime-col...

Actually, that one doesn't use the geolocation API. It's just a realtime mapping example.

This one uses the geolocation API: https://github.com/leggetter/realtime-visitor-tracker

It's actually a really good use case, but not the only one.