While I agree with Jesper Johansson's view that discouraging people from writng down passwords just encourages them to reuse passwords across systems, I don't think passwords should be written down. Instead, they should be printed. Print not just one password but tens of them scattered across a page. All but one will trigger an alarm and lock all the doors nearby automatically.

3D stereograms (aka Magic Eye) could be a fun part of the solution too so people will have cross their eyes to signin. LOL.