Set up an nlocktime transaction.

Essentially, it's a dead man's switch. A transaction that can only be executed at a future date, and if you're not dead by that date, simply send the funds to another address that only you have access to.

I'm not sure if this is something that is available with every single blockchain though. For alts, you'd probably have to go with a custodial service, or simply trust your will recipients with a private key (hide it somewhere perhaps).