This application allows you to send a message to somebody, indicating your current position.
Wait until the integrated GPS detects your location with a reasonably good precision, then hit the "Send Message" button.
The application will automatically compose a SMS message containing your current coordinates: Latitude and Longitude.
You will then be prompted to send it to any person of your choice.
The receiver will be able to retrieve you, simply inserting these coordinates in Maps, or any other equivalent application.
NOTE: requires iOS4.