Actually, when I put up that last link I thought of a much simpler way:
Use this to detect the board shaking when your dog steps on it. Just tape or glue it to the wood.
Then use an Arduino to control, and the enclozed Piezo to make a beep!
You can find tutorials and an online workshop on our tutorials that will walk you through how to use an Arduino and how to read from sensors such as these:
