I'm pretty sure this is trivially implementable in CHDK [1]. Already, with the hacker-enabled RAW mode (this is on Canon P&S cameras), it saves a RAW copy of th

I'm pretty sure this is trivially implementable in CHDK [1]. Already, with the hacker-enabled RAW mode (this is on Canon P&S cameras), it saves a RAW copy of the image to the SD that never shows up in the camera browser. If you delete the JPG using the camera, the RAW file is still there, but not visible to the camera. So what you'd want to add, for safety's sake, is to make the camera save this RAW in a custom format (and folder and naming structure) that is inconspicuous, but can be read by your custom RAW software. E.g. save the RAWs in some scientific data format and say you're a student and those files are from some old class assignment you had to transfer. I estimate it would take a dedicated hacker less than a month to put together on their spare time. Without transmission capability, you can never guard against deletion (they could just confiscate or destroy the SD). [1] http://chdk.wikia.com/wiki/CHDK http://chdk.wikia.com/wiki/CHDK