warning light came on on my wife's 2008 expedition EL
I have not had it up on the lift yet but the brakes seem to work just fine.

what kinds of things will trigger the brake warning light?

 

The BRAKE light should just mean the fluid is low, or the park brake is on. The ABS light is the scary expensive one.

 

ABS light has been on for 2-3 months
fluid is ok, parking brake not on, rotors and pads are good

 

I think you can get a scanner that will read brake codes. I don't think the standard OBD-II reader will do it. You can probably borrow one from a part store and find out what is triggering the the light. I think each wheel has a few components that will trigger that light.