German researchers are working on self-lacing shoes for elderly people. They’ve developed what they call the most practical gadget for harnessing kinetic power from shoes.

While there have been several attempts to turn walking into a power source, they’ve usually been impractical. According to researcher Klevis Ylii, previous attempts have not only been too bulky to fit in an ordinary shoe without bits sticking out, but even with this bulk they’ve only produced 250mW, which can power a light but is well short of goals such as charging phones on the move.

Instead Ylii and colleagues at HSG-IMIT decided to keep things as small as possible and target ulta-low power applications. They’ve maximised the efficiency by using two different devices, both fitting into a modified shoe.

One harnesses the power generated by shock waves when the heel hits the floor, while the other harnesses the power of motion as the foot swings. Both use what are effectively tiny generators, using the power to move a magnet within a stationary electric coil.

The devices combine to produce just 3 to 4 mW, but the researchers say they’ve identified a couple of possible uses. One is as a motion sensor that tracks both movement and direction in the feet, which could be used for rescue workers in an unfamiliar, dark or smoke-filled building.

The other is for a self-lacing shoe for people who struggle to bend down easily. The idea would be to power both a sensor to note when a foot entered the shoe, and a small amount of force to tighten the laces.

Of course, a generation of movie lovers will be hoping they turn this into reality by 21 October: