Inductively coupled plasma spectroscopy (ICP) is an example of a flame test used in real life. You probably dipped metal ions into flames and they turned green or red or purple. In ICP spectroscopy a sample is heated to 3000K or some really hot temperature and the sample will emit a specific wavelength of light. The machine has a diffraction grating that separates the wavelengths of light and detects each of them and their intensity. Therefore you can use ICP to determine what substances are in a sample and how much. It's used for analyzing things like lead content in drinking water.