Today, I see this article about a new Symbian smartphone application called "Mobile Mouse". It does exactly what I suggested someone do for a hack. However, their camera mode is smarter than my idea -- the movement is done by rotating your view around, so you can hold your phone in your hand and tilt or rotate it to move the cursor.
I'm amazed. While I doubt that my suggestion was the root cause for this program, it makes me wonder what would happen if I suggested that someone write a program to bring about world peace. Unfortunately, I don't have an actual technical suggestion on that one.