One of the showpieces of MI:RN is an attempt by Ethan Hunt to free-dive (meaning swimming without an auxiliary oxygen supply) into a water cooled computer.
The necessity for the free-dive is predicated by the pretext that the sensors will detect 'any metal' (notice we're not just talking non-conductive or non ferrous, but any metal) that passes through the intake.
With this in mind, how is it possible for Ethan to have an electronic interface built into his suit, indicating his remaining oxygen supply?
Whilst it's a relatively simple component, is it possible to create such electronics without the use of metals?
Is this based on an existing technology?