It literally only takes 3 momentary soft touch switches, 2 1N4001 diodes, a stereo jack, and wire along with an enclosure to make.
Now you can have both of your preset modes, bank up, bank down, tap tempo, and set the 3 switch to do whatever you want. Mine is currently controlling infinite delay!
What's even cooler is that you can really set the 3 switches up to do anything you want with a combo of Ring Tip and Sleeve in the edit menu.
I found the project through this site:
http://forgivenick.wordpress.com/2010/0 ... pedal-diy/
It includes a link to wiring as well as detailed hi-res pictures of the dude's build which was super handy in wiring up mine.
Here is my build of it:

It only costs about $20 to make. I'll be sure to document the insides for everyone.