Now what?

How do I make this?

Via an old Evhead post:

Tonight I stayed up late implementing a cool new Blogger feature. I’m using it to make this post right now. From anywhere on the web, I can right-click and instantly bring up a Blogger form, populated with a link to the page I’m on, plus any text I have selected. A little edit, and a click, and it’s posted here.

Anyone have recommendations on how to build this? Is it just a bookmarklet? Where I’m stuck is that rather than posting to Blogger or another CMS I’d like to post it to my domain (does that mean I have to create my own CMS first?). Any pointers would be appreciated.