"whose only runtime job is to sit in the communications path from the primary software to the avionics hardware and monitor the outputs of the primary software

"whose only runtime job is to sit in the communications path from the primary software to the avionics hardware and monitor the outputs of the primary software and ensure the values and/or rate-of-change in certain values are within some physics-based sanity limits before they hit the hardware" Brings to my mind: Erlang