I like the idea of putting one in your will (that's essentially giving it to an attorney, though, isn't it?). You could also have fun nesting these, if you weren't afraid of mind-blowing complexity -- split the secret into M-of-N, and then fragment some of the pieces further. It would allow you to create asymmetrically-important fragments, so that each piece really just represents some fraction of the secret, some pieces worth more than others.
This M-of-N system is a great feature and it will help many people, including myself sleep better at night. But . . . .
Since the subject of super paranoid people has already come up here, If I were that paranoid person, I would prefer a backup system like X+ M-of-N. Where X is the piece that is in my will.
I want to die before any of the pieces can be used. Is that something that could be possible with the current system that you're working on?
As I typed that out, I answered my own question. I think it is possible, if you split it into enough pieces and keep > 51% of the pieces required to recover your wallet for the will.
Example: Require 7-of-10 and put 4 pieces in your will.