Matrix’s PowerWatch 2 is a watch that can be powered entirely by the sun, or even the user’s body heat.

The crowdfunded, wearable device supports both thermometric and solar charging, meaning it never needs to be plugged in to charge.

It uses a 1.2-inch color display, with a rugged body and a solar cell ring protected inside the bezel – this allows it to store power not only from outdoor light but also works indoors.

The device shows the user how much energy it’s receiving from body movements at any given time.

It can be pre-ordered for $199 (£156), with the price expected to increase to $499 (£391) when it is released in June 2019.