It's a browser extension that monitors my purchases (like plane tickets) to compute a carbon footprint, then sells me the ability to purchase offsets, or recommends behavior changes?

Really interesting idea, I could see this doing well.

I'd personally need a ton of detail about how it collects data. If anything is sent back to a server then I'm out, the industry lost my trust by misleading about data sharing/usage. Also need a ton of data about the offset I'm buying, and what sort of cut the app takes from that purchase.