Tracker shows your iPhone's current position in your Web site. All you need is a website and a standard FTP account to access it.
And this is how it works: Tracker keeps sending an HTML file with your position and a Maps link to your website using FTP in intervals of 20 seconds, if new or more accurate position data is found (provided network is available).
You can activate a screen lock for avoiding changes by unintended touches. This will also prevent your iPhone from falling to sleep