Gives the recipient of the SMS the ability to track the sender from their current location to your current location (where the SMS originated from). This is helpful if someone wants to find you by just following the directions you have sent them via SMS from the BackTrack app. They can then just follow the route to your location in the Google Maps app.
Directions can also be reversed if you want to track back, starting at your current location to where the SMS originated from, by simply selecting the "reverse" option in the Google maps app itself - This is helpful if you parked your vehicle at a big shopping mall, sent yourself the location from where you were in your parked vehicle and later want to track back to your vehicle.
Other uses include - tracking where you pitched your tent at a Mighty Men conference. Where you parked your vehicle. Animal darting location. Track back when exploring. Geotagging locations for Google Maps...the tracking possibilities are endless.