As many folks continue to look skyward in expectation of drone delivery services, they're missing the development of an increasingly popular delivery technology back on terra firma. Wheel-based delivery robots may not be quite as sexy as their flying counterparts, but with fewer regulatory hoops to jump through than drone services, the technology is likely to become more widely used sooner rather than later by companies looking to make their delivery operations more efficient. The latest outfit to join the race is U.S. startup Refraction A.I. with its autonomous Rev-1 machine. The brainchild of University of Michigan professors Matthew Johnson-Roberson and Ram Vasudevan, the Rev-1 tootles along on three wheels instead of the four or six that we see with most of the competition. The wheels and storage compartment mean the look of the Rev-1 is similar to efforts from dominant player Starship Technologies, as well as delivery robots from FedEx and Amazon.