Major Tom:
As IRRenewal says "RNP" is in a way a state of mind, and not a physical 'box' (like that of a DME or VOR).
State of mind? No. Performance based navigation (PBN) that in theory is not tied to a specific sensor; yes.
But, as a practical matter the present sensors are GPS and secondarily at least one IRU. Further, there has to be at least two FMSes, sometimes three, and for lower RNP values a tailored EGPWS/TAWS. Roll steering is also required instead of CDI steering for RF legs. And, generally for RNP values of less than RNP 0.30 a roll steering autopilot must be used, and probably with a second autopilot available.
That is a whole lot of hardware.
Each OEM has some latitude as to how they make their airframe qualify.