This is a example of profiletracker.us (its a paid tracker at $5.00 a month)

Now when you click little IP button at the top right you are taken to MaxMind. For this one this is what I saw:

Then when you click on the little Firefox/IE logo button at the upper right it will analyze the persons browser string. What is a browser string? Well it will give you information on the persons computer. Its just one way to better identify the person. Like you can see if they are on a PC or Apple, what operation system they use (XP, Vista...) and some of the goodies they have installed on their computers. Here is what you see when you hit that button:

Then there is the button for "HITS". Some remember hits when it was a site open to everyone. Now the only way you can use HITS is to be a profiletracker member. Hits will look over their myspace. If its public or on your friends list then you can see if they have any trackers. You can also use it to get some more info that you might not else see. Its a awesome tool to use. Here is a example of what you can see with HITS:

edit (additional info): Now if that person is in their data base it will show who they are (meaning someone identified them or they were tracked with a older code that positively identified them). One other thing I really like is that you can search their data base to see it they ever tracked a person by either IP or myspace ID so that is a sweet feature. Is it a perfect tracker no but I am very happy with it. I would say it identifies (correctly) 75% of my hits. If it doesn't have that IP in the data it will do a "likely match" via their PC info which I find to be about a 50/50. Either way I think it is defiantly worth the $5. a month (after all what is that a trip to Mc Donalds).

BONUS with profiletracker.us is that you get to use HITS (hide in the sky) which allows you to get more information on a profile

For more information on profiletracker please see this thread: Profiletracker.us