My guess:
it's a wire feeder--you attach it to the end of the EMT run, and when you feed the fish tape through it comes out the bottom of the handle. The wires then follow the fish tape back in the pipe, making a smooth bend at the top of the handle.
With his thing, maybe you could get away with a one-man pull for small wire (if you set the wire spools up right and are lucky).
It could be improved with the addition of a bottle at the top of the handle, like the hopper on a drywall texture gun, that would drip pulling lube onto the wires as they make the bend & enter the pipe!
Cliff