I got myself a second-handed Mooer Hustle Drive mini-pedal, a Chinese clone of the Fulltone OCD.
Overall, these little pedals (I also have an Orange Ninety and a Green Mile) sound really good, are really well built and take very little space on the pedalboard. All that for an affordable price.
One odd thing I noticed with the Hustle Drive was that the Volume control was almost unusable: the pedal has a huge gain when the Volume knob is set fully clockwise, and it becomes attenuated enough to reach unity gain (same level whether the pedal is on or off) at around 2 or 3% of the knob position (on the CCW side), while the rest of the travel has little effect (massive gain throughout).
Pierre built a controller for his guitar setup, using a computer as an effect box (it also seems possible to use a Raspberry Pi). Effects are modelled with PureData, the audio is routed using Jack and the controller’s brain is an Arduino.
Eli Hughes made this awesome PCB pickguard for his entry in the Freescale Kinetis Make It Challenge. It contains a Freescale Kinetis ARM Cortex M4 processor with DSP extensions to process the guitar signal, providing both an analog and digital audio output.
He also release a video with the details of all the maths and physics explained, as well as the hardware design.