Lifesense (3.5e Feat)
From D&D Wiki
You see the light that all living creatures emit.
Prerequisite: Cha 11
Benefit: In addition to any normal light that might be present, your surroundings are illuminated by roving points of brightness created by living creatures. To your eyes, a Medium or smaller creature gives off life force sufficient to provide bright illumination in a 60-foot radius, revealing itself and all features and objects in range to your life-adapted sight. This life-light behaves like regular light--you can't see into solid objects or past solid walls. A Large creature gives off life-light in a 120-foot radius, and the radius doubles again for each additional size category larger than Medium, up to a maximum radius of 960 feet for a Colossal creature.
Normal: You cannot see the light that all living creatures emit.