SPOT2 already has a feature with their 'Track' program, additional annual charge, that allows you to establish a shared page online with contacts.

You set the page up based on the dates of your trip, (from 1-30 day duration). Each time you activate the Track program it automatically sends a ping to the online map every ten minutes. It does this until you manually discontinue the Tracking function or turning off the unit.

You can also Name the page with the title of your adventure and add some personal information.

I have done this with hikes and ultra runs so people, especially a nervous DW, can see where I am at on my course. It would certainly establish a a digital trail for SAR, which is why I also have this function.