No secret agent device worth its name would be complete without a self-destruct mechanism. While we can't quite make the Pi disappear in a puff of smoke, we can rig a sneaky booby trap that will eliminate all traces of our secret agent setup if the Pi were to get caught behind enemy lines.
First we are going to encrypt our entire home directory. Since we've been doing all of our pranks and projects inside the pi user's home directory, if someone were to read the SD card on another computer, they wouldn't be able to get any valuable data from the card except for a pretty standard Raspbian installation.
Then we'll add an optional wipe trigger-mechanism, which can be initiated either locally from a USB keyboard, or remotely via SSH, that will erase our encrypted home directory and replace it with an empty, innocent-looking, and original home directory.