When it comes to the "realistic goal" part of doing challenges like these, I think the one hangup people have is that if it's a realistic goal, chances are it's already been implemented somewhere, making the entire project somewhat less interesting to pull off. But I definitely understand, modesty over promising the world to Element14.
As for the Caltrans example, that's a good idea. Just a cheap, easy indicator for people to be like, "oh shit, hearing loss is a-coming!" I don't know if that's what Element14 is looking for, unfortunately. They kind of specifically say "consumer" (see: not industrial) device, so I'm not sure if this would fly.
I'll pose some questions at the next SOHW meetups.