As/if it grows in popularity it will be interesting to see what private enterprise comes up with to help end users.
I.e. many people have non-OEM exhausts and will want to know before getting points and prizes whether they are in the danger zone. Phone sound meters are obviously inaccurate, and so perhaps something akin to the cheap breathalyzers will come into existence. A once specialist expensive bit of kit becomes a cheap accessible bit of kit. Or maybe it would be just a service, or rolled into MOT finally.