1. Can you give me an example? Is it like the following scenario?
Let say you are on Twitter, then select "cappuccino", then search "cappuccino" on Twitter using Google. And the result should be this: "https://www.google.com/search?q=site:twitter.com+cappuccino"

2. I implemented another add-on as a test "Selection Context Search - mini #1". This will add just one search engine in the context menu. Is this what are you looking for?