I recently saw on a friends phone a db meter. So I'm thinking one certainly must be available in software.
 
I do question the accuracy of a phone mic, but I don't know. If there is such a thing what type of mics might work?

I did some research into that awhile back, after seeing the person sitting next to me on a plane using one. But I gave up on the idea when I found out that no two smartphone-based SPL meters gave the same readings. Those little 50-cent microphones aren't exactly reference-quality transducers. Plus not all devices allow software to turn off the AGC circuit, which is essential.

Kind of what I expected with the phone thing, but did hope any decent mic would work with software. I'm sure there would have to be way to calibrate.
 
may just have to get the real deal one day. thanks

I have a hardware SPL meter that gives readings with A or C weighting and find my iPhone software meter also with A or C weighting to be just as accurate.

Mind you my readings don't have to have truly great precision.