I did a brief search and didn’t find anything like this, so here goes:
The idea is to rig up a barbell with one held in place and the other end weighted(much like the way people do their homemade t-bar rows) and lie down on the floor and press it, one handed, from the weighted end.
My reasoning is that it wouldn’t be more stable than a dumbbell press (unstable in every direction), but less stable than a standard bench.
And even though there’s probably a seated chest press that does the same thing, this would look slighter hardcore-er.
Has anyone tried this? Was it useful?