[Shlomlom]

When I use my Westone um2 with the iPhone I sometime want to use the iPhone mic to hear the surrounding without to remove the earphone.
Do you know an app that open up the iPhone mic? (I know I can dial out or record, I'm looking for a way to only open the iPhone mic without another action)

 

[Gorktastick]

Yes!   Check out the app called "Awareness".  It seems to be exactly what you are looking for!  I use it all the time when I walk into a coffee shop or store so I can talk to people in front of me without having to take my IEMs out of my ears.  I have tried it successfully with every set of micd sets that I own.  Hope that helped.