In addition to https://, ftp:// protocol identifiers, the i Phone also supports tel://, facetime://, and mailto:// You must have a complete and valid URL (Uniform Resource Locator) for it to work.
tel://NUMBER will pop up a dialog asking if you wish to make a cellphone call to NUMBER using the baseband.
facetime://CONTACT will pop up a dialog asking if you wish to make a video call to CONTACT using Apple's Facetime over Wi-Fi.
Note that this ability is similar to the assisted GPS feature of the i Phone 3G and i Phone 3GS, with the difference in that turning ON Location Services lets i Phone and its applications use this tracking info immediately (less than 10 seconds).
Turning it OFF means this tracking info from the cell towers is simply not processed on the i Phone, but is available if needed.
Similarly, IMEI, in combination with a SIM card, provides an easy method to track the location of a person.
Changing cellphone, you can be tracked by SIM card used.
The result will be either 0 or 1, depending on if the flag is set or not.
These defines are predefined OR-combined mode flags.
Unfortunately, changing IMEI number is illegal in many countries, but is possible on the original i Phone using homebrew software.