As I understand it, it's a plastic membrane keyboard which has a resistor matrix (and the usual contact points) screenprinted directly onto/into the membrane plastics with a conductive ink. Sort of the same X-Y principle as old (resistive) touchscreen panels, though tangled up (and maybe layered) like a regular key matrix. By measuring voltage drops between sets of keys (through an ADC input in the keyboard controller chip) and comparing the differentials against a little (firmware coded) lookup table, you can effectively duplicate the functionality of a full (or lots) KRO diode-matrix layout. Diodes are really cheap, but screenprinting in mass quantities is even cheaper, plus typical cheap**** gutless keyboard microcontrollers already have ADC input lines (previously dedicated towards debounce, I think, though that's not necessary with this sort of implementation). Microsoft already has at least one such keyboard on market (one of the SideWinders, I think); their marketing spin on it emphasizes that it's "superior" to mechanical keyboards (insofar as the context of comparing it's NKRO "antighosting" against selected 2KRO mechanical models).
I'm not sure, but I think the tech can (with a beefy enough microcontroller) also measure relative key pressure as well. Maybe it's what MS uses in that multitouch/accessibility prototype thingy they announced a year or so back.
Maybe it's called a Resistor Grid Membrane or Resistive Key Matrix or whatever. Doesn't change the fact that it's still a membrane keyboard which lacks any sort of real keyswitches. Great if you spill liquid on it, otherwise blatantly inferior even compared against rubber polydomes. Cheap and disposable, welcome to the future.
