They say this means you will get the clear sound without any background noise, not that anyone else is trying to do something similar... Jawbone anyone?
In "stealth" mode the HX1 uses an ear sensor to to convert your vocal vibrations into speech rather than using the external microphone. Moto claim that because their sensor is on the ear rather than the side of the skull you get a better quality sound.
No details of a US release yet but the HX1 will be available in Asia in July [Motorola]