You could structure it as a browser extension - it'd have the ability to run on certain sites (or sites you click the icon on, or whatever) but not all sites an

You could structure it as a browser extension - it'd have the ability to run on certain sites (or sites you click the icon on, or whatever) but not all sites and definitely not all your local data. But also, I was thinking mobile apps actually make sense here. They are actually isolated between each other. Some publishers are not be respectful of data you explicitly share with them, but you still have to explicitly share it. I'm a lot more comfortable giving my bank password to a mobile app (preferably an open-source one) that runs locally than to a website or mobile app that sends my credentials remotely.