As someone who has used Lastpass in the past, a feature I really appreciated was that you could "require password reprompt" for certain sites before the password could be accessed. So even if your vault was unlocked, for your most sensitive passwords (think financial accounts), you could require that your master password be provided again before it could be copied or form-filled.
It's not clear to me if this was cryptographically enforced, but even if not, it is certainly a nice-to-have last ditch protection against the "nosy person who comes across my computer while my vault is unlocked" case.
Does this feature exist? Is this something you have considered?
1Password Version: 6.x
Extension Version: Not Provided
OS Version: OSX
Sync Type: 1password.com