Walking the dog, popping out to the shops, going sightseeing … it's not that wheelchair users can't do these things, it's just that they're a pain in the butt. Or, more often, a pain in the shoulder ...

On today’s episode of “so simple it’s brilliant” is the Firefly from US-based company Rio Mobility, an electric “handcycle” that snaps onto a wheelchair and replaces the need for the occupant to push ...