If I'm SRTing, I have a hand ascender with a foot loop with me. If I'm one-sticking, then I have two long continuous loops, a hollowblock, a tether, and a lineman belt. Either way I am going to secure my lineman belt to the tree and attach above my belay device to unweight it. From their I can switch to my backup.
Been practicing this in the backyard. The only thing I can't figure out how to get out of is my rappel rope failing, but at that point I probably would stay put and call home.