Modifying Transcend WiFi SD Card Firmware

Potential use case: turn a simple printer equipped with an sd-card slot (to print photos directly on the printer) into a manual wifi printer. The job would be converted to, say, jpeg, sent on the sd-card and then you would have to print it manually.

Other use case: be able to send any file to this SD card, this way you could easily transfer pictures, videos and music to a non WiFi multimedia device, like a TV Tuner, MP3 Player, etc...

I also like the idea of having a tiny, relatively cheap, long running deaddrop wifi hotspot on batteries. Any idea of how long you could run it for from a button battery?

Could you create a half decent mesh network / wifi repeaters with these taped at various locations?

I could imagine a wifi hacking linux distribution like xiaopan might be quite fun too, or something with tunnelling / vpn that can connect to a hotspot and make it safe.

If there were some way to add a few sensors to it without making it much larger / power hungry, that could be really cool, especially considering how much space you have for logging.

I'd like to see if one could be surreptitiously built into a usb cable, or wall wart, so it's powered when the usb cable is plugged in, but otherwise there's nothing obviously special about the usb cable.

http://www.creative-science.org.uk/mobile_LED.html

Of course, that's a tiny amount of power but it's still there to be harvested.

Not sure what the legal situation is. In England an "artist" was asked to remove their installation of flourescent tubes in a field below power lines. They similarly harvested power. (I can't find that case using Google :-( but here are plenty of others https://www.google.co.uk/search?q=fluorescent+tubes+power+li... )