For the Paris-Brest-Paris last August (1,200 Km in <90 hours), it gave my better half much tranquility to see me moving on his computer/cell phone. We used RideWithGPS on both of our T-mobile Samsung phones along with WhatsApp for free instant messaging. Each of us had to pay USD $6.95 for RideWithGPS' basic service for the instant tracking. If you trace the route on the computer, it will automatically show up on RWGPS app on the cell phone. You then share the route with your friends (who must also sign up to RWGPS). It works amazingly well, especially if your family/friends track you from their computers. Since it was a short time, we only signed up for a month with RWGPS. Battery life is an issue but I carried 13,500 mAH power bank. It gave enough juice for about 48 hours of continuous use of my cell phone (cellular network, GPS tracking and even background lights on at night to make sure I was staying on course.)

There are satellite services like SPOT Personal Tracker, but it's a lot more expensive. This is a favorite among bike tourers venturing into remote places of the world with no cell phone service