The one linked by dalmatiangirl61 did have an outrigger of sorts and for loads of 500# or less a simple trailer jack will do.When do you use something like this?
I can't think of a use for it and I perpetually load and haul stuff on the bed of my pickup (flatbed).
At one time I saw a clean looking headache rack for a flatbed that was actually a light duty knuckle boom. Pretty neat I thought, but not all that useful without outriggers.
You guys ever used a crane on a service truck without outriggers? Go ahead- Try lifting 500 lbs 10 feet out. See what happens to your 15K lb truck lol.
The advertising pictures of these little hitch and pickup bed cranes lifting stuff is hilarious. "Look we lifted a 100 lb welder 6" shy of getting it on the tailgate!" "Look we lifted a generator a 12 year old girl could set in your bed!"
A resourceful scrapper friend of mine has a an old Peterbilt cut down to a single axle tractor he uses to haul weird 5th wheel trailers that are built for wrong to be hauled by double axle trucks. He added a wet kit to it, a pair of hydraulic winches and outriggers behind the cab. He built a gin pole setup with a 5th wheel pin and pads that locate it on the frame. He uses that regularly to self load messed up trailers and recover vehicles off the road. Scale that idea down to a pickup with a gooseneck ball in the bed and I think you'd have something worthwhile.
But really, 99.9% of the population just uses a tilt deck trailer with a winch to pick up craigslist deals that the seller can't load. They might even haul their skidsteer with forks or just bring their mini excavator out, leave it chained to the trailer and just load whatever it is with the bucket.
Like when I bought my scissor lift I wasn't sure if my trailer had the clearance to load it so I rented a scissor lift trailer from the local rental yard for 2 hours for $40.
All much simpler solutions that some clunky, borderline useless hitch/bed crane thing. You see a newer pickup with one of those and it's like the badge of a Harbor Freight platinum club grandpa.
A friend had a work truck used to service heavy equipment and it did have an engine hoist type of deal with an electric winch. No outriggers were provided. It was however much more heavily built than a typical pickup truck.