I'm using PAMUSB to lock my RPi, which works fine. When the USB Stick is pulled, I use xscreensaver-command -lock to lock the machine.
Here comes the tricky part, I can't quite figure out yet. xscreensaver comes with several slideshows, but pretty much all of them suck because they insist on useless transition effects. Also I can't use any GLX modules ( e.g.