I've been experimenting with the cheap spectrometer, and boy is it cheap, as far as I can tell seems to work. Unfortunately, it has shown me nothing useful. All the LED LCD screens have a near identical output of a high blue peak, and lower red and green. The plasma tv I tested was much more balanced.
It did show however, that despite the smartphones being set to what seemed like a similar brightness to desktop monitor, they were infact significantly brighter.
Desktop monitor Benq BL2405, -30% blue light mode enabled
Old Iphone (not sure which, still had a 4" screen)
IMO Q2 Smartphone
I'm going to try some physical and software overlays later and see how the spectra change.