I interviewed a guy for a dev job a while back who had written software for a consumer embroidery machine just because he had one and wanted it to work better,

I interviewed a guy for a dev job a while back who had written software for a consumer embroidery machine just because he had one and wanted it to work better, that had turned into a pretty good side business and it sounded like he had the same customer base, and it was a very profitable niche. A small but devoted group of users who weren't well served by the manufacturers and didn't have the technical skills to develop a solution for themselves.