Researchers waste time navigating paywalls when trying to access papers. An extension could automatically check open-access repositories when users hit a paywall.
The tool would integrate with major publishers' sites, detecting DOI/PMID and querying Unpaywall-like sources in the background.
Universities might pay for institutional licenses to reduce their students' friction. Individual researchers would use a freemium model.
Start with basic DOI lookup from arXiv and institutional repositories. Expand to more sources later.
Risk: Publishers may block the extension or change their paywall detection methods.