My favourite solution is the timelock dead man switch with nLocktime, which is described
in this thread. The problem is that the popular wallets don't make it too easy to create this kind of transactions.
Another problem is that you don't know when you are going to die. Let's assume you want to leave your coins to your children. You set up a timelock with nLocktime at a future block around the time you will turn 70. But if you suffer a heart attack and die at 60, your children will have to wait 10 years to get access to the coins. It would be great if timelocked transactions could be edited to broadcast earlier upon showing the needed cryptographic proof. I don't have much knowledge of the subject, maybe they already can.
I don't know if you ever wondered what would happen to all your email addresses and online accounts if you die without leaving your backup passwords to your family members or lawyer.
I have heard of examples where Facebook has given the parents of a missing child access to their Facebook account in order to see if they can retrace their last steps or find some clues from the messages with their friends. In a way, social media accounts are inheritable. I don't see why that couldn't work for email accounts as well.