Quoting cheekychimp:
^^^ Oh Knocking sounds, smoke from under the hood, pieces of engine on the highway ... what do you need a warning light for when you have all those tell tale signs /ubbthreads/images/graemlins/rofl.gif
DSMLink & AEM both allow you to set yourself up so that if you're logging all your sensors/gauges you can set up an idiot light on the dash (check engine light, other add on light, etc). Frankly I don't want to have to constantly monitor gauges because it draws attention away, I just want to know if something is going wrong ASAP. If I'm not looking at a gauge and it starts to go bad, I may still kill the car.
As such, I set nice conservative levels for badness, and when that light comes on I get out of the throttle- usually makes the light disappear.
The system works well and the lack of gauges makes the car less of a target IMO. That said I still keep mine in the glovebox for tuning purposes.