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.
nLockTime transactions do that now - they allow you to sign a transaction that cannot be accepted onto the network before a certain block height. If you decide you don't want that transaction to go through, move the coins to a new address, and issue a new nLockTime transaction.
I don't see how this would protect your coins if you were in jail. All this would do is move your coins to another address for you while you are locked up. This has nothing to do with protecting your coins nor with you being able to access them after you get out.