There's also the DeBroglie wavelength of an object.... Basically, modern physics says there's not really a difference between particles (matter) and waves (energy) -- just the way they behave. Really tiny, fast things like photons generally behave as waves (light), but occasionally have particle-like interactions. Not-as-tiny, not-as-fast things, such as electrons usually act like particles but occasionally act like waves.
Nowhere near as tiny, nowhere near as fast things such as Oldsmobiles are pretty much always particle-like -- but theoretically have wave properties too. Hence, the wavelength of Superman can be calculated. The DeBroglie wavelength is Planck's constant (6.626 x 10^-34 J-s) divided by the momentum (in kg-m/s). That might be something akin to what you're looking for -- Fred's tracers contain something with a unique DeBroglie wavelength, and his device can home in on the associated frequency. Forgetting of course that with the right momentum, any object might temporarily have that frequency. And if it just happened to be the wavelength that Superman has at his usual flight speed.....
Black-body radiation , IIRC, is based on Wein's Law -- any object emits light over a certain spectrum, clustered around a wavelength which is proportional to the inverse of its surface temperature. At human body temperature, it's basically all infrared -- theoretically we should emit some visible light too, I think, but it's way too dim to see. (Though when a fanfic says that Lois was glowing after a kiss, it may be literally true, if the kiss were hot enough!) This isn't specific to objects, but to temperatures -- it's why you have to supercool infrared telescopes, so the telescope's own emissions move out of the infrared and don't cloud the view. This is also how the "measurements" of a star's surface temperature are obtained.
Ah, Dr. Smith and Dr. Godwin would be proud.... ;-)
