I wonder if an App could be coded
that would send the highest dBA noise spike possible
over the cell phone network?

I have posted before about trying the official
NIOSH dBA noise app for Apple iOS phone/iPad

https://www.cdc.gov/niosh/topics/noise/app.html

and trying to home test accuracy cheaply.
I ended up finding that you needed to use the microphone in the original Apple corded earbuds,
and tape the year 1994 “Storm Whistle” I already had in my White Water emergency kit

https://www.stormwhistles.com/frequently-asked-questions#q4

to a blower nozzle as the noise generator which did measure 118 to 120 dBA.