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A tiny radioactive battery could keep your future phone running for 50 years
(www.techradar.com)
This is a most excellent place for technology news and articles.
A lot of sensors/gauges in industrial applications are retrofitted with lorawan or similar remote readout capabilities right now. Battery life for these devices is already a big design consideration, especially since not all locations are easily accessible.
With a power source like this you would essentially charge a capacitor, use the stored charge to do a sensor read and short data burst, and then wait for the next charge.