The design files are now in this repo: https://github.com/spro/blinkinch. It includes the Eagle schematic and board files plus a .zip of gerber and drill files

While I wait for the PCBs to arrive from OSHPark I'll use an equivalent breadboard to start developing the firmware and driver.

My current conception of the driver exposes a service with a single method:

setRGB(r, g, b, message=null)

Scripts can go about their business (e.g. poll the bitcoin price) and call the service when they want to display some information (e.g. setRGB(255, 0, 0) when the price is declining). The optional message parameter can be used to explain the change, potentially showing up as an unobtrusive notification (like Growl).