This would be where you could have 3 watching only wallets installed and it would tell you that a multi-sig payment could be redeemed by 2 of 3 of them.
You could also allow creation of a spending transaction that each private key owner could sign in turn.
This is better for "boards" that have N of M spending requirements. Each member would have a watching-only wallet for all keys associated with the cold store and one set of private keys.
You could also create 2 level shamir sharing. For example, you could have 2 of 3 sharing, but each share is then split up into 2 of 3 as well. This means that each share is protected against loss too by sharing.
This is already supported by the lockboxes! All parties in a lockbox can be offline keys, created separately and independently. Each party individually manages their own wallet holding that key, including all the regular methods we have backups... yes you can do a 2-of-4 lockbox between 4 parties, and each party can do a 3-of-5 fragmented backup of their individual wallets (which hold the key).
Speaking of that, we're working on multisig lockboxes on the "devel" branch -- anyone can check it out and play with it. It's actually looking really good. Got P2SH working, so you should be able to go above 3-of-3 on mainnet now... but of course I don't recommend using any money you can't afford to lose (yet)!
The lockboxes and all the data passed between devices/parties assumes that all keys are offline, and thus always contain all information needed to sign offline. The downside to this is that all these message formats have changed, even for regular offline transactions, so all online & offline devices will need to be updated to use this. But once you do, it does work!
Will have the last couple pieces of it implemented soon and put out an experimental build to get people playing with.