Here's how I solved my desire for a helmet mounted microphone, that's dirt cheap and works very well.
I have an iPhone (but any phone could use a similar process), which I use with a pair of UltimateEars
UE-11 pro headphones. There are a lot cheaper alternatives to the UE's but once you've made the investment, you'll never go back. They also have the bonus feature of eliminating wind noise, since they are custom molded to the ear canal.
My issue was adding a microphone so I could receive calls on the bike or make calls without having to take my helmet off. I was not happy with bluetooth or in-helmet microphone/ear speaker sets. I wanted something really simple.
I purchased an iSoniTalk microphone ($20 list), which provides a microphone and a jack in which to plug any headset. Here
is an independent review.
I have two helmets. One is a Shoei Multitec flip-up and the other is a Shoei RF-1000 full face (mostly for trackdays). Here are all the pictures:
All I did was to lift the left cheek pad and place the iSoniTalk cable underneath. Then I clicked the cheek pad back into place. Holding the cheek pad down, I pulled on the cable until the microphone was snug with the cheek pad. This provides support for the microphone and causes it to stand up. It also keeps it out of the way so the faceplate can flip up and down without interference.
All you have to do is then plug the headphone jack into the microphone jack. Plug that assembly into the iPhone and you're set. I thought the cable length would be too short but it turns out to be perfect.
Microphone sound quality is good (identical to the stock iphone earbuds). The bonus is that the microphone has a button to answer or end calls. I tried both my lightweight and heavy (winter) riding gloves, and with both I can easily flip up the face-shield (with the visor flipped down) reach through with the left gloved hand and press the button. No need to touch the phone. It can stay in my jacket pocket nice and safe or mounted on the RAM mount I have on the left bar. Usually I just leave the phone in my jacket, but on longer trips I will want to power it in the RAM mount cradle.
I have a Zumo 660 mounted to the right bar. I still need to test how it all works together (bluetooth to the Zumo). As soon as I get my Russell seat back I think a long day of testing is in order.