Under a grant from MIT in Cambridge, Mass., students at the Alabama School of Mathematics and Science in Mobile are working on a roving robot that can detect land mines. Their device is based on a toy — a battery-operated Power Wheels jeep made by Mattel Inc. — but it is hardly a plaything. The students are outfitting it with an infrared sensor, a metal detector and a computer to search for all-too-real and deadly devices.They chose an inexpensive vehicle to make the detector more affordable than the heavily armored devices in current use. However, they don’t want it to be disposable. They are engineering it to stop before it runs over a mine and to signal for sturdier equipment to come in and detonate the explosive.It is sad to think that young people must focus their talents on countering malevolence, but heartening to know that they have the vision and technical skills to do so.