There’s a couple ways to make the RealitySuspender work outdoors. One would be to install a large swingset in your backyard… but with no swings. In the middle of the swingset, attach the hook.
Another way to do it, would be to have two tall posts, and a rope connecting them. Imagine that you bought two used basketball hoops on Craigslist. You set them up in the backyard, and tie a rope connecting the baskets.
In the middle of that rope would be a knot, with a hook in, that you can hook the bungee cord to.