Sounds expensive
Really? A battery with 50 years of continuous output? Or 2000 years for C14.
I dare you to find ANYTHING which will deliver that power output over the same amount of time.
By the way, medical tech and spacecraft are not the only obvious application. Black box locator transmitters come to mind. Something which will transmit once in a few minutes an ultrasonic ping does not need a lot of power, but needs it continuously until it is found. Using these means no more 4 week rush until the battery runs out the way it had to be done (and failed in either case) for MH370 or AF447.
Biting the hand that feeds IT
