External Microphone in Headphone Jack? There are some external stereo microphones for IOS that plug into the headphone jack rather than the dock connector. For instance, the IK Multimedia iRig MIC Cast.

They claim that they work on Android as well.

Well, they may work, but do they provide better sound quality than the internal phone microphone, turning it into a decent digital recorder for music, for example? (with the right software, of course).

My question isn't really whether those microphones are better quality than the internal microphones, as I assume they are. But does the headphone jack on Android phones (mine is the Galaxy S4) really provide the input capability for better quality sound, including in stereo?

Of course that jack can transfer sound in both directions, headset and microphone, as it is a phone. For output, the phone provides quality stereo music output to headphones, as modern phones are also music players. However, the microphones on phone stereo headsets are generally low quality monaural microphones only suitable for phone calls, usually not better than the internal microphone, might be worse.

So the question is--is the input function of that jack capable of providing quality stereo input, if one has a quality stereo microphone attached? (No matter how good quality the microphone is, if that jack really cannot transmit that quality sound, but reduces it to a very low resolution and frequency-reduced monaural sound, no point at all in attaching such a microphone.

Anyone know about the input capabilities of the headphone jacks on Android phones. (If it varies from phone to phone, then how about mine, the Galaxy S4?)
I found this video on YouTube: Galaxy Samsung S4 External Mic for mobile phone.  and here is the mic quoted on eBay. I plan to test it soon. It seems the vendor has positive feedback.

It is noise-reducing microphone for the 3.5mm jack. I tried to check if the cited video has stereo sound. I believe it does, but I am not sure it did not come from some YouTube stereo enhancement, so I cannot claim it for the microphone. I plan to use it for lectures, so it should serve for the purpose well enough.