I have a GoMuddy harness and it comes with an ascent/descent rope you leave on the tree at your stand. you just clip on and slide the prusic knot as you go up. in the event of a fall at any height you're connect to the fall restraint at all times. http://www.gomuddy.com/shopping/Departments/Safeguard-Harness.aspx

they don't show the A/D line in the video but it does come with it.