As an inventor, 15-year-old Grayson Rosenberger has seen his share of misfires. Take the combination Go-Kart-skateboard that his family simply calls the "death-mobile." Says his dad, Peter, 43: "He comes up with some bizarre things, but he hit one out of the ballpark with the leg."

The leg in question is an artificial limb that Grayson sheathed in Bubble Wrap and packing tape and molded with a heat gun. The covering mimics the shape of a real leg and solves a very real problem faced by amputees in poorer countries.

"In the Third World people are looked down on for being amputees," says prosthetist Jim McElhiney. "A cover like Grayson came up with helps them blend into the community." Moreover, it costs $15 as opposed to the $1,000 such a prosthetic might cost in the U.S. Says Paddy Rossbach, president of the Amputee Coalition of America: "I think it's a fabulous idea."

The Nashville eighth grader, whose leg won him a $10,000 prize from the company that produces Bubble Wrap, didn't have to look far for inspiration. His mother, Gracie, 41, is a double amputee who lost both legs in a car accident 24 years ago; she and his dad run the Christian-based charity Standing with Hope, which provides prosthetic legs to Ghanaians in need. "I remembered my parents told me about a boy named Daniel who broke his leg playing soccer and had to have it amputated," says Grayson. The charity could only give Daniel, also 15, an artificial leg without a cosmetic skin covering, but because the disability is so visible "he's made fun of in school," says Grayson. "He's mocked in the street."

Those days may soon be over. When Grayson and his family return to Ghana this June, the first thing he wants to do, he says, is "make a leg for Daniel."