HTML5 Geoloaction

HTML5 GeoLocation

I know there's an app for this but I would like to learn how to do this.
When I upload my code onto the server it can find where I am in realtime with geolocatin.
But if I would like to monitor someone using the geolocation, how would I go about doing ths??
Do you need to download a Google API or something??

So if I am currently at location A and personXY is at location B. If I was to look at my monitor, how do I see personXY on google map in realtime.
Any tips or advice would be greatly appreciated.

Here's my code, that only monitors myself

<!DOCTYPE html>
<HTML>
<HEAD>
<TITLE></TITLE>
<script src="http://maps.google.com/maps/api/js?sensor=false"></script>

var watchID; 
   var map;                      
   var mapMarker;

if(map) {                           
         map.panTo(latlng);
         mapMarker.setPosition(latlng);
      } else {                            
         var myOptions = {
            zoom: ZOOM,
            center: latlng,
            mapTypeId: google.maps.MapTypeId.ROADMAP
         };
         map = new google.maps.Map(document.getElementById("map_canvas"), myOptions);

mapMarker = new google.maps.Marker({
            position: latlng,
            title:"You are here.",
            clickable: true
         });
         mapMarker.setMap(map);
      }

}   
</script>
</HEAD>
<BODY>
 
<div id="map_canvas"></div>

</BODY>
</HTML>

How do you expect to know where that other person is? Are they wearing a GPS beacon on their head?

Or are they "checking in" using some phone app?

my final product is have a phone app that can track a certain person's location.
I know there's an app for this already but I would like to learn how to do this myself.
There are millions of people out there. How do I monitor person X with my phone??
Does he and I need to have a google API or something so we can be in sysnc with each other??

I checked the web and google dev page and they don't have anything on how to monitor someone's location for the phone.

Of course not. How could your phone track someone else? Can your phone tell you where I am right now?

The only way to do this would be for the other person to have a phone or other device that would record his or her location in your database (or somewhere else accessible).

I'm confused - do you want to do this with a native app, or via the HTML geolocation API? Both are possibilities, but your question mixes both, and so can't easily be answered.