Battery-free watches aren't some newfangled invention but something that has been knocking around for several decades. They operate on the principle of a thermocouple, generating power from the difference in heat between your wrist and its case. The problem with thermocouples, however, is that they're normally too weak to drive anything but the lightest and smallest of motor.

Enter Matrix, who has now, with some nifty tweaks, built a digital watch that can accept basic Bluetooth notifications. The PowerWatch X can even generate enough power to drive a vibration motor, letting you know when you're getting a call. Plus, it'll even do basic fitness tracking, notifying you on how many calories you've burned while you're out and about.

The company isn't resting on its laurels, however, and is now working on its latest project, an Energy Harvesting Sensor Beacon. Imagine, if you will, an internet-of-things device that'll never need to have its batteries replaced, and you're pretty much there. Matrix has found a way of ensuring that, like its watches, its sensor platform can use thermocouple-based power to function.

For all those internet-of-things devices that currently use coin-cell batteries, or require recharging on a regular basis, it's a big deal. Especially for companies that use a lot of sensors at once, like the sort to control the climate in large offices or in sensitive installations, like power stations.

The company won't be ready to begin manufacturing until half way into 2018, and there's no word yet on how much it'll cost. The PowerWatch X, though, is now open to pre-orders for $249, and should be available very soon.

Nathan Ingraham contributed to this report.

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