My brake indicator bulb flickered on my W124 when the brakes wore down on the front, as if there was a slight amount of disc warpage...went away with new front pads...I don't think my rear pads were equipped with sensors though...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car