I thought about creating a service, like boomerang for gmail: Person signs a transaction from A->B, but doesn't broadcast it. My server will broadcast the transaction only if you don't check in for the last 30 days. If you get thrown in jail (or die), no one would suspect that transaction is yours.
Wouldn't a Dead Man's Switch work for that purpose? But those are mostly for emails only. If there was an email-to-broadcast-tx service, that would work with almost all those dead man's switches or even google inactive account manager.