Creating a mobile-friendly page on an integrated site (i.e. doesn't use a theme)

I’ve successfully integrated a WP blog into an existing site, forgoing the use of themes. On this site, mobile devices are served from a subdirectory. I’d like to create a mobile blog page, but the only solutions I’ve found are plugins that detect a mobile device and swap themes.

Are folks delivering mobile-friendly content on sites that aren’t theme-based?