Looking for a Specific app

[m3rr]

I've googled and searched

I'm looking for an app
that allows me to use my Android as a Speaker and a MIC

For example

Let's say I have music playing on my PC
I can hear it through my phone

Or Msn messenger running a Voice Call on PC
I can use my phone to speak through


I know I'm asking a lot just curious if anyones hear of this?

Much obliged.