Dead man's switch

Some online services offer one. In April 2013, Google launched its Inactive Account Manager: if an account went unused for three, six, nine or 12 months, as its owner chose, Google would first warn them by text message and email, then delete the data or share it with people they had picked.

In bitcoin, the switch can be built with a timelock. The wallet’s script has two paths: the everyday one, with your key or keys, and a recovery path, with a key held by an heir or kept as a backup, that works only once the coins have sat unmoved for a set number of blocks, up to 65,535, about 15 months. Checking in means moving the coins to a new address in the same wallet, which starts the clock again. If you stop, because you’ve died, fallen ill or lost your keys, the recovery path opens, with no company or court involved.

It has costs:

• Each check-in is a transaction, with its network fee.
• The clock can’t tell why the coins stopped moving. If you forget, the path opens while you’re alive, so its key belongs with someone you’d trust with the money now.
• An open path is no use without what goes with it. Whoever holds the recovery key also needs the wallet’s configuration and the steps to follow.

A dead man’s switch decides when a key works, not who inherits: that’s for a will and the law. The guide on inheritance goes through both sides, and the entry on probate explains the legal one.