You might consider a color temperature light meter. If you are a professional shooting images in industrial environments, inside and outside, then knowing the correct temperature is critical. Oh, many homes now use CFL type of lights, incandescent lights are becoming more difficult to purchase, those too project fluorescent light.
Many modern digital camera allow manual setting of degrees Kelvin. Of course one can chimp their camera LCD, but that 3 inch LCD is very inaccurate, it is a JPG rendering of the raw file, also doing so is time consuming. Using a color light meter one meters the light, sets that Kelvin number into the camera.
Color light meters are expensive, thus for the non-professional it may not be worth owning one. Yes, shooting in raw one can correct white balance, but that is not the best for the image. But for the professional, the best results come from capturing the color correctly in camera, then using post processing for tweaking, not correcting mistakes.