This is probably not new but it might be helpful. I took an old part of a Treesuit that was used to attach to the tree and used it to attach my tether. It locked it to the tree and I moved all over the place to try to get it to move and could not. This is only 9 inches (guess) and it worked great on the tree in the pic which is about 18-20 in circumference. I tried it on a much bigger tree and it was not long enough. I think a climbing sling that is longer could serve the same purpose and could be doubled up on smaller trees. I am sure others have found ways to lock the tether in place.