Hi Majsalten,
The MSDN Windows Store apps forums are for developers to discuss how to write their own apps. For questions about using Windows 8 please post
in the Windows 8 forums on http://answers.Microsoft.com .
That said, I don't believe an app such as you describe will work. Apps in the background cannot generally record sound, although it may be possible to leverage the background communications features to do so.
--Rob