this one was recommended to me by Analbumcover and it's working quite well:
App Shopper: Glympse - Share location with friends (Navigation)
Basically it will fire up a text message to anyone you ask it to, sharing your phone's location for a certain period of time (however long you want it to be, up to 4 hours) and how you are moving. The text message (could also be an email fwiw) contains a link to a website so the recipient doesn't even need to have the app install, or even know what the app is, as long as they can go on the web. If you set a destination, the app will even give you an ETA.
For me, it'll be pretty useful when I go out running since I always run alone. That way, I can fire up a glympse to my wife as I head out the door and she'll know if I'm still moving and heading back home without getting too worried. Also works when I'm out and I just want to send her a quick message that I'm heading back home. I decided to install the app on her phone too, so I can even request her to share her phones location...
FM