We carry colorimetric CO2 detectors with every BVM county wide. They don't get used very much due to the fact we have so many people on scene that the waveform cap is already set up prior to intubation.
They are still required to be present during intubations in the event that the inline on the monitor fails. I have seen one used exactly once, and that was by an overzealous medic.
If I place an SGA by myself (unsure when that would happen), I am supposed to use one instead of the monitor as the state has deemed me too stupid recognize the mere presence of a waveform.
I used one earlier this summer when my filterline EtCO2 adaptor got fouled w/ already aspirated vomit 20 minutes into a code. It was better than nothing.