Google has a dead man switch of sorts - after set time of inactivity it can be setup to transfer all rights to someone else via email. Its not perfect because you would need to camp out for half a year of course. I wonder if other services let you do that? As for key distribution among friends - there has to be some smart solution relying on the fact that your home server isn't there. App hosted on amazon that will call your home lab, perhaps your number? Even a freaking buzzer in your house! And only after it fails all that it would release some control, perhaps one extra human remambabre password away from full access? I believe UKs nuclear deterant submarines have checklists to ensure UK is well and trully gone before firing any nuclear missles. I don't know how much is available on the subject, but surely this must be a common problem, when you broeden it's scope.