SRT (Single/Stationary Rope Technique) is a great add-on for one-sticking and rappelling. Once you have climbed a tree and setup, you can leave your rope and come back the next day or later on the same day and climb right back up the tree using SRT. Only requires a few extra components as long as you already have a device like the Madrock Safeguard or equivalent.
You can also use these kits as a guide to build your own SRT kit if you would prefer to use a different quick link/carabiner or foot loop.