GMaps.js supports HTML5 Geolocation:
GMaps.geolocate({
  success: function(position){
    map.setCenter(position.coords.latitude, position.coords.longitude);
  },
  error: function(error){
    alert('Geolocation failed: '+error.message);
  },
  not_supported: function(){
    alert("Your browser does not support geolocation");
  },
  always: function(){
    alert("Done!");
  }
});
      GMaps.geolocate supports 4 functions:
      
success (required): fires when geolocation has been successfulerror (required): fires when geolocation has not been donenot_supported (required): fires when geolocation is not supported by the browseralways (optional): fires always after every scenario described above.