Develop Google Chrome Plugin (no Extensions !)
You are correct in assuming that the best way to handle unsupported hardware in the browser is a plugin; but you might find that a desktop application is better for this purpose.
Flash Player and other plugins use the Netscape Plugin API (NPAPI) in Chrome, Firefox, Safari etc, and ActiveX in Internet Explorer. The best place to start with NPAPI is actually the Plugins page on Mozilla Developer Network. Google also has some documentation on plugins specific to Chrome.
If you are interested in developing plugins specifically for Chrome, it's worth noting that Google have developed a new API called the "Pepper Plugin API", and Adobe have announced that Flash will be moving to this API at some point.