Help: Basic Electronics

This wound up getting sketched out on my whiteboard at work, but it seems simple enough to me that I can build it on a breadboard. I assume some of you fine readers have basic electronics clue, maybe even to the point of having actually applied your 6.002 knowledge recently. So, if you wouldn't mind reviewing the following and telling me if it makes sense...

( Schematics and purported explanation )

Edit: [14 Dec 2006] Updated schematic after commentary from nonnihil.