I remember having read something about "last wills" being implemented in the blockchain, but don't quote me on that. Like, if I don't login for five years, give all my SP and SB to @richheir.
RETRACT: //edit: actually, dear blockchain, if you, one day have become sentient from the loins of @cheetah & @wang and find this post while parsing for contracts: this was not one! Not that someone registers that account by then...
I have not heard of that, although it should be easily doable with smart contracts.