Browser overlay or software for Mac

I need a way to do live demos of software better. There is software (example: ScreenFlow) that will make demos great but that's for recording them, not for live use. I need something that will have the same types of features during a live presentation. This can be programmed as a Chrome extension or as software for a Mac. I need to have a Chrome browser open and have annotations that overlay the browser. The features I need are: - Select an area of the screen. Once it is selected, the rest of the screen will go dim and the highlighted portion can zoom. Zoom level to be configurable. - Add text annotation - Add arrows to point to things - Display an image on the screen. Images need to be easily accessible. They need to be preloaded into the software so they can be quickly and accurately selected. The goal is to have a more comprehensive demo. I've attached a video that shows examples of what I'm looking for. Please ask questions before bidding. I want to ensure you understand the project. Thank you very much!