You can simply encrypt your seed with a password (or use a split seed) and write this password in your will left at a notary or in a sealed envelope given to relatives.
True, and that's a good system for someone who does not have anyone they can trust. But if you do have someone you can trust, you don't need to do this. It also doesn't help in the situation where I suffer memory problems but am still very much alive, which happens to literally millions of people a year.
You can also schedule a mail to her birthday for example, and cancel it every year if you are not dead or amnesiac, or you can simply use a service that allow your heirs or trusted people to access your datas after your death or after being inactive during a given amount of time, like
this one for example.
I would be very careful trusting any third party with any part of my recovery process. A regulated lawyer is maybe acceptable - a service ran by one of the worst offenders when it comes to privacy (Google) definitely is not.
So what will you do, if someone is able to imitate your voice and ask her by phone to immediately send all your funds to a given address because you've been hacked and you are away, for example?
Well, first she couldn't, because my back ups are not in one location, so it would take her time to recover all the necessary pieces in order to gain access to the wallets. Secondly, she's not an idiot so that wouldn't happen. There are literally thousands of questions she could ask to which only I could answer to confirm it was me. And third, if this was a realistic prospect, then there is nothing stopping the same thing happening to all our fiat accounts too.