Using chrome extension is silly, because then you can just have whole wallet in it and not bother with checking. The checker is valuable on mobile devices where extensions (and local static html files) dont work or poorly. Perhaps android app using webview?
You can already download carbonwallet as a chrome extension. So this monitor app would be for people who use the wallet online.
I've sent you pull request which merges everything into single html file, so it's not as much broken as MyWallet (which checks script tags - that is actually pretty useless because it's easy to inject code living in an anonymous js closure of setTimeout and delete the tag).
Verification is trivial, just xhr the index.html and compute hash for it.