2-year old Alejandro had Spinal Muscular Atrophy. Medical insurance wouldn't cover a powered wheelchair until he was 5 years old. That was unacceptable to Shea, his father, who bought a wheelchair on eBay and modified it so that Alejandro could control it with his feet:
After unsuccessfully trying to repair a broken digital kitchen scale [Shea] was inspired to reuse the sensors as pedal inputs. [Alejandro] has limited foot strength and the sensitive strain gauges are perfect for picking it up. Above you can see the sandal-based interface he built. The two feet working together affect steering as well as forward and reverse. The pedal system is connected to the wheelchair using a Digital to Analog converter chip to stand-in for the original analog joystick.
At the link, you can watch a video of Alejandro maneuvering the wheelchair.