I actually came up with the idea on my own, but noticed it was somewhat baked already.
It serves the same purpose, but more reliably. The problem with a sign-reader that actually reads the font type, color, etc. is that it relies on line-of-sight. If there is any interference (rain, tree branches,
it won't work and you'll still get that ticket. Bluetooth works through *walls*, I just tested it again a few seconds ago to make sure I'm not spewing bullshit.
What I propose is a speed limit gauge in the instrument cluster with a constant-on (when the vehicle is running) bluetooth device that autmatically pairs with a constant-on bluetooth device embedded in speed-limit signs when you come within 50-100 feet. The bluetooth sign sends a message to your gauge with the current speed limit. This would work the same as sending messages between bluetooth-enabled cell phones, which require the phones to be within 30 feet. I'm certain the range could be increased with a stronger power source, such as a solar panel like the ones they use for road construction signs.
Sounds an ascending tone for increased speed limit, descending tone for decreased speed.
I admit this is just a better method of achieving an oft-baked goal, but I believe it is better than any methods I have seen thus far, and uses different technology, and thus warrants it's own posting.