Author here! It was quite a surprise to see one of my old posts on HackerNews.
For those interested in what happened next: I managed to build and run sqlite, rsync, and dropbear SSH on the SD card using buildroot: http://buildroot.uclibc.org/
I quickly moved onto other interests as I couldn't work out any practical applications at the time.
Feel free to reach out to <me AT fernjager DOT net> if you have any ideas, or want to pick my brain on this project.
The SD card has a script that monitors filesystem changes, and would push the images via curl to the client connected to it through WiFi.