Some tend to forget, and then reappear. So it was with mono, is a block with an external headset. Appeared on the market almost simultaneously with the classical headsets, enjoy a certain popularity, have been consigned to oblivion once again interested producers in the year 2009. In 2010 the trend continues. I think that such devices might be interested, primarily, those who are accustomed to dealing with a wired headset and do not want to wear the ear of some device. Many people like. In particular, I do not like to walk down the street with a Bluetooth-headset, and if it's doing something purely for testing voice quality. So, imagine your attention yet another headset - a compromise.