A group of researchers in Germany have created two shoe-sized devices that make it possible to charge electronic sensors by walking.

The first device, called the "shock harvester," produces power when the heel hits the ground and the second, dubbed the "swing harvester" generates power when you're swinging your foot, according to BBC News.

Both gadgets take advantage of the energy generated when magnets move past stationary coils, which induces a voltage and the birth of an electric current.

The swing harvester measures about three inches long, less than an inch wide and half an inch tall, and was originally designed to power a pair of self-lacing shoes for the elderly, Live Science reported. The shock harvester is a little bigger, weighs about a third of a pound and was designed for indoor navigation systems, which use sensors to collect information about people's location and then send it wirelessly to a computer.

"For the indoor navigation system, there are sensors [accelerometers] within the shoe that determine how fast you're moving, acceleration and the angles that your foot has traveled. And from this data, the system can calculate the path that you have walked," said Klevis Ylli, a doctoral student at the Hahn-Schickard-Gesellschaft Institute of Micromachining and Information Technology in Germany.

The research team tested the devices with a participant who walked on a treadmill, finding that the person's walking generated enough electricity to power an attached temperature sensor and a wireless transmitter inside the shoe that sent temperature data from the sensor to the participant's smartphone, Live Science. Ylli said this mesh of technology could give "smart shoes" the ability to keep track of distance, speed and steps taken the same way fitness trackers can.

Ylli added that his team is looking to make improvements to the harvesters so they can collect more energy from your stride.

The creation was annonuced Wednesday in the journal Smart Materials and Structures.