Browser Add-On for Scrapping specific page

What it is required is to develop a Browser Add-On / Plug-in that identifies when a specific website is accessed, in a specific page, and when specific data is shown, allow the user to push the "Capture" button to get HTML and push it to a SQL Server database. It looks pretty similar to the Amazon Assitant, that when you are browsing different pages, identifies content and shows related productos in AMAZON... but easier, because it will be only for 1 website and the HTML just need to be extracted and inserted in a SQL Server database table with some other data like datetime stamp and an ID Number. It must work for Chrome and Firefox at least (Edge / Explorer if possible) when intalled at least in Windows, but other O/S would be desireable (Chrome or Firefox on Windows / OS X / Linux ). The "target website and page" must be able to be changed on code.