Holy Baader-Meinhof Batman! Just yesterday I had the idea for a phonecase that had a few buttons on the back-- nothing so specific as a chordic keyboard, more for things like a camera shutter button and some other macros. I even started roughing out a schematic. The FaunchPad looks sort of ill suited for the task because its wired but there are some good BLE SoCs out there now that can sip power.