How about a credit card sized HP15C clone made of titanium? https://www.swissmicros.com/product/dm15 https://www.swissmicros.com/product/dm15 People who want

How about a credit card sized HP15C clone made of titanium? https://www.swissmicros.com/product/dm15 https://www.swissmicros.com/product/dm15 People who want solar power on everything don't understand how shitty the sun is as a source of energy compared to a small pot of chemicals. The real thing you should be going for: small hydrocarbon fuel cells (theoretically much higher energy density than lithium). Or I guess, very well programmed, very energy efficient microprocessors; good luck with that in current year.