Google pay per click

I ran across some google pay-per-click users today, and after some research, I realized google has been testing this since roughly Nov. 2005 - it has been a while but i never see such option available in my adwords account.

How will it work? Personally, I am shy to ask the other party to call me, i don't feel comfortable before I get to know more about the vendor.

But it is said Pay per call is a huge market.

We'll see.