It's a brilliant/evil hack; it works by getting the expression source from the frame and building an AST from it. Lazyweb request: LINQ. (PyNQ?) ;)
Behaviour-regulating designs: the supermarket tile thing I posted the other day is one, but also websites that make it hard to leave, reduced visibility at roundabouts to improve safety... the list goes on.
Tiles -- Supermarkets used to have a trick placing slightly smaller tiles on the floor in the more expensive aisles of the shop. When a customer entered on of these aisles their trolley would click faster making them think they were travelling faster and thereby subconsciously slow down and spend more time in that aisle.