I bought the IMM-6 for measuring the frequency response of in-ear-monitors (IEM). With a simple piece of hose as a coupler with the IEM this works easiy with the FFT iPhone app. The results cannot be compared with a professional measurement but for comparisons they are very useful.
The 3,5mm female connector is a little tight on my model, and the microphone came apart when I tried to pull off the coupler. I was able to fix it.
For the price it is still a great option, and I recommend it, you just have to be a little careful.