Run by the Toyota Mobility Foundation together with Nesta's Challenge Prize Centre, the Mobility Unlimited Challenge recognises the best new designs that improve the lives of people with lower-limb paralysis or paraplegia.
Announced at at tech show CES today, the five finalists have each been awarded $500,000 (£398,000), with the winning designer, which will be announced in 2020, set to be awarded an additional $1 million (£796,000).
The shortlist includes Moby, a bike share scheme equivalent for electric wheelchairs, devised by Italy's Italdesign.
The scheme would enable people who use lightweight manual wheelchairs to slide them into an electric-powered pod when they want to cover greater distances.
Italdesign wants to enable wheelchair users to travel more easily using the scheme, which would be accessed through the same app in cities across the globe.
Two exoskeleton designs feature on the shortlist — a wheelchair hybrid called QOLO (Quality of Life with Locomotion) by a team from the University of Tsukuba in Japan, and Quix, which enables walking movement, by US groups IHMC & Myolyn.
QOLO is a lightweight mobile exoskeleton that users can operate while sitting, like a standard powered wheelchair, or from a standing position.
"Our device gives users the choice to sit or stand, using cutting-edge technologies," said Kenji Suzuki from Team Qolo. "This means that wheelchair users can interact with other people at the same eye-level, improving communication and changing the way they see the world."
Quix, meanwhile, is a wheel-less device with motors at the hips, knees and ankles to move the legs in a walking motion.
It uses perception technology from self-driving cars and control algorithms for balancing autonomous humanoid robots to deliver advanced mobility, safety and independence.
The Phoenix AI ultra-light wheelchair by UK company Phoenix Instinct looks like a more conventional product, but it packs smart functionality beyond what is seen on the market.
Made of lightweight carbon-fibre, the manual wheelchair has sensors that detect if the user is leaning forward or back, and it adjusts its centre of gravity accordingly. This makes it easier to push and turn, while also stopping it from falling backwards.
The wheelchair also boasts intelligent power assist and automatic braking. Phoenix Instinct founder and CEO Andrew Slorrance is motivated by his own experience as a wheelchair user, having sustained a spinal injury at 14.
"By the time I was 16, I'd decided that I would one day design a wheelchair that would change perceptions by using cutting-edge materials and styling," said Slorrance.
"I knew the next step beyond advanced materials has to be to make wheelchairs smart. But that costs a huge amount of money in development," he continued.
"So, when I saw this Challenge, I thought, here is the money to develop this technology "No-one else is going to do it. No company is going to decide to spend half a million dollars on research and development to advance the manual wheelchair... This Challenge changes that."
Another of the participants in the competition, Pierluigi Mantovani, co-founder and CEO of Evolution Devices, was inspired by his father's experience with multiple sclerosis, which caused foot drop.
Evolution Devices' Evowalk is a non-intrusive sleeve that fits around the user's leg. Sensors track the user's walking motion, enabling the sleeve to stimulate the right muscles at the right time to help their gait.
As well as improving their mobility on the spot, the Evowalk sleeve has a rehabilitative effect over time.
"[My dad] was recommended a device that was far too expensive, so myself and some friends built this prototype that helped," said Mantovani. "After that we wanted to make something affordable for others. Our main goal has always been to help people regain the ability to walk freely again."
A panel of expert judges selected the five finalists in the Mobility Unlimited Challenge from 80 entries. Following the further development of their prototypes in collaboration with end users, the grand prize winner will be announced in September 2020 in Tokyo.
Carmaker Toyota founded its Mobility Foundation in 2014 to support the development of solutions in transportation and personal mobility. Its projects have included the IBot stair-climbing wheelchair, the Human Support Robot to assist people with everyday activities and the Concept-i Ride vehicle with joystick steering.
Toyota's partner in the Mobility Unlimited Challenge is innovation charity Nesta through its Challenge Prize Centre. CES, the Consumer Electronics Show, is the biggest tech trade fair of the year. It runs until 12 January in Las Vegas.
Images by Simon Mckeown with Craig McMullen.