Google has indexed thousands of publicly accessible HP printers
Idea for startup.<p>1. write a script to scrap google links to HP admin panel<p>2. filter out the IPs that are from US (given you want to work on US market)<p>3. assemble the list of printer types and current toner levels.<p>4. write a script that will print to each of those printers a one single page, stating your company "Cheapo Suppliers Inc" was notified that "your printer is low on toner. Call xxxxxx to re-fill. Lowest prices quaranteed within one day delivery!". You can add link to your shop page that already redirects user to specific type of printer they have, some type of one-click order (based on which toners are low).<p>5. daily rinse repeat.<p>6. sell your business to HP (at least try to).