I actually built my own controller footboard, using an Arduino.
I've got 24 buttons, a 10" TFT screen, expression pedal (can take 2). Since it's completely custom, I've done things like put in a metronome which flashes on the screen and sets the tap tempo, control over the looper and a bunch of other cool things. For example, after selecting a patch with a button, hitting the same button will set an alternate config for that patch (adding an effect, such as a boost and delay for leads).
It can also mute piezo outputs on my stereo guitars. It can control relays if I want to do bypass looping with pedals. The display screen is incredibly useful, too.
I started with virtually no knowledge of MIDI and little soldering experience... if I can do it, you can. On the other hand, it's been a buttload of work, so unless you enjoy tinkering, it's probably not a good idea. On the plus side, I can do anything with it I want.
I'll post pics.
Richard.