Yes, the n800 and n810 have lock codes you can set (it comes with a default lock code that you can Google) so be sure to change it. Once enabled it will ask for it every time at start up. Without it you cannot access the device even if you plug in the USB connection. I believe you cannot flash it either without the lock code (after enabling it).

Unsure of SD cards however, people could always eject them so don't put anything on the SD card that you want to keep private.

Good luck, I took a class on domestic violence, and in the second semester I worked in a domestic violence shelter. So I know a little about how hard it is.