Interesting question about this that I'm not 100% on.
Do iPhones constantly search for wifi to join or only when setting is open?
In onevenue where I have one 2.4ghz mic I only have 5Ghz wifi installed but assume that devices that can connect to both 2.4 and 5ghz will sporadically scan either and cause some sort of interference, even when in someone's pocket or purse.