I had the same failures. I naively bought a camera with no external mic thinking my phone would work fine and I could use the mic from my hands free kit. WRONG!! Just way too sensitive no matter WHAT I tried. And I couldn't find ANY apps that gave up enough control of the gain settings to actually make it useable.
Plus, unless you're recording in 24 bit WAV, the noise floor is so high that when you get home and try to bring the volume back up, you just get loads of noise.
Ended up buying a Tascam sound recorder. But having 2 record buttons to push got old, so then just got a Drift! So in all, I ended up wasting a ton of cash! #Winning