If your kick drum pedal breaks or if you just want the feel of a real drum set this is how to build yourself a kick pedal pad and sensor. I do not go into detail about the pedal build but mainly into how to build and wire the sensor.
Step 1: What you will need
First you will need a piezo transducer from Radio Shack #273-073 $2.19 This is the gold disc you see in the pic with the red and black wires coming off of it. the transducer has been removed from the black housing that it comes in. Be careful while removing it as to not bend the disc or pull off the wires.
The silver disc you see is the lid off of a regular can of canned vegetables. Don't ask me what size. I don't know. It is about 3.5" in diameter. This will transfer the vibration to the piezo transducer.
The two black squares are rubber pieces cut from a mouse pad just larger than the can lid. Any flexible rubber or foam cushioning material will work here that is not to thick.
Lastly you will need a 1/4" instrument cable. you will cut one end off of the cable and strip the wires back to find the center conductor and the ground shield conductor.
A little duct tape and epoxy and you are there.
Update: After using the pedal for a while I was getting to many "double triggers" so I did a little more work on the sensor. What I ended up using in place of the mouse pad rubber was the thin cardboard from the back of a notepad (not corrugated). This seems to work very well and I do not get any double triggers now.