Faber Acoustical makes some pretty cool iOS and Mac apps. I got them a while back when they were a little cheaper but they’re still reasonably priced. Since I always have my iPhone on me I use these apps pretty often. More often than I would use Smaart on my laptop.
There’s an RTA app that I use the most. Granted the iPhone microphone doesn’t have full range, flat response, but you can still identify frequencies that are feeding back or sticking out. When you’re killing feedback it helps to really zero in on the exact frequency that’s giving you problems. Many times when dialing in by ear it’s hard, or at least a lot slower, to get perfectly center on the problem frequency.
Once I’ve gotten enough gain from a microphone then I can move on to adjusting for tone. That’s how I approach problematic situations like wireless LAV’s and headsets or choir mics.