Plug-in for limiting who can view one particular post?

Is there such thing as a plug-in for restricting who can view a particular post or page, without requiring people to register?

Maybe like this:

I enter a list of my permitted viewers’ email addresses (only about 20 friends; I already know their addresses), and then to view the post, those people simply enter their email address in a box on the page.

Sort of a quick-and-simple security step which I fully realize is not truly secure because there’s no password or registration involved but that’s OK.

An alternative might be a plugin that allows you to password-protect an individual post or page; I would simply send these 20 people the password. Naturally this is less secure since theoretically they could share the password.