I don't think that we need to have items like that. We already have the ziplines. As both methods would require to be out of combat, there's not much benefit in teleporting.
I'm not against teleport items, but they should be more interesting, than some one button "back to base" item.
Your "Watcher's Door" could be much better, if it would allows you to create two temporary portals like the Doorman's 2, but with some downgrades/differences in order to not make it an alternative.