I have an 07 Trailblazer that has started clicking when I press the brake pedal. No lights are burned, and all fuses are good. I can also feel the click in the shifter (AT). Any ideas? The car is still under warranty
I have an '04 and it has always “clicked” when depressing the brake pedal but mine sounds more like a relay activating and I do not recall ever feeling it in the shifter. I’ve always suspected it was for the brake lights or perhaps the trailer wiring. I can check it tonight on my way home if that’ll help. Here’s a great site dedicated to the TrailVoy platform- http://forums.trailvoy.com/index.php
The click that you hear is the interlock switch that prevents you from shifting out of Park unless the brake pedal is depressed. The noise can be considered to be “normal”, and is not something to concern yourself with.
Now why didn’t I think of that? 
I have no doubt you are correct!