Lightbulb [Q] Bluetooth Microphone (No Earpiece) For Android

Hi all,

Will keep it simple here, looking for a mini bluetooth microphone that will clip to my shirt and link to my phone (OnePlus One). I have a pair of earphones that don't have a mic (they're Sennheiser IE800's so I don't plan on changing them), and I also own a Sony SmartWatch 2. I can answer calls on the smartwatch but have to take the phone out of my pocket anyway so that I can talk to the person calling.

So I was wondering, if I have my earphones plugged in and I answer a call on my smartwatch, is there such a thing as a mini bluetooth mic only that can replace the phone microphone during a call?

Any help or other solutions for this problem would be great.

Thanks,
Michael