Age Verification

Hi everyone,

I’m looking for a plugin that requires every viewer to first click a link to verify that they are over the age of 18, but also allow search engines to index all pages without this verfication.

Is there anything like this out there?

If not, could someone recommend a way to do this?
I am a decent programmer, but have never explored the WP-Core or written a plug-in for WP, but sure I could do it with a little direction.

Thanks,
Jared