Seems like with all of the talent on here someone could make one thin enough to go under an I-Beam axle. Wouldn't need wheels or a handle. Could be used as a jack for flats or roadside repairs. I used to have a gadget that screwed into a spark plug hole and could be used to air up tires. Always carried tire irons, patch kit and a spare tube. Didn't have enough money as a kid to afford good tires
Years ago I bought an air jack pillow type that had been marketed to Mercedes owners It was only about an inch and a half thick, about 18 inches across and you blew it up by sticking the inflater hose over the exhaust pipe. after about 10 years setting on a shelf I GOT IT OUT AND THE RUBBER PILLOW WAS ROTTEN. IT LEAKED DOWN TOO MUCH TO USE..
HERE'S A LINK TO A NEW ONE https://www.youtube.com/watch?v=lOmAe-WKQmo