A free service for cellphones, called Glympse, lets you share your location in small increments of time. By fall, it will be available for most phones.
This software from Android Market shows where you are on a map and will allow you to share your location by sending a Glympse to a person or people. It’s available for blocks of time up to four hours. Selecting four hours means recipients can track you for that period, no matter where you go, including the speed of the car. You can share your location with a business partner, client or your family.
Glympses can also include a short message.