Basically, the key components are:
- silicone buttons
- adafruit neotrellis pcb, which handles the button presses and turns on the pretty lights
- raspberry pi, which runs a python script to control button colors, and relay OSC messages to SL
- usb audio interface, for audio in/out
- sooperlooper
By far the most fun though was designing the enclosure and making it with a laser cutter. I'd never used a laser cutter before, and oh man, it was a lot of fun. Took a lot of trial and error, but it was worth the multiple trips. The bonus is that I'm now a lot better working with Illustrator than I was before!
Here's the final product:

I will try to share a video once I have it all up and working. The last piece I'm trying to finish is getting midi sync working, so that I can integrate it into my synth setup.
Code and more details are on github. Hope it helps someone!
https://github.com/mobeets/loop-baby