Vibro? - It had occurred to me too that using a blunt ended chisel intelligently might work well. I'm not so confident I could use it that way on a bleed nipple without snapping it off though. I think it would work well on more substantial fixings though. The big advantage of the dedicated sockets is the way, as you rightly mention, that the vibratory force is applied, through the specially shallow socket, to the fixing not the body of what it's screwed into. For the number of times I would use them they would be an expensive luxury - BUT I WANT ONE.
