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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.
My grampa had a pacemaker that was.
Edit: Source - https://osrp.lanl.gov/pacemakers.shtml
Edit2: For the smoke detectors, i know its not what powers it per se, as far as the electronics that sound the alarm and such. More pointing out it contains radioactive material, and is something in every (hopefully) house, and you likely walk by it often.
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That is well cool