Ask HN: Software recommendations for creating website demos?

What I'm imagining is that you would preselect a few html elements and add some labels. Then, when demoing, you should be able to hover over these elements to active "focus mode": the rest of the screen blurs, and your label pops up. Or maybe you can use your arrows to move from one highlighted area to the next. Like a Prezi for live websites. Does anything like this exist?