The device itself seems pretty chunky, perhaps almost 1" thick. The design won't likely make it to the American or European markets, as it might be more of a niche item, even in Japan.
The Japanese market is more suited to the device as they are generally more conscious of air quality. In Japan, many travel to waterfalls or running streams, where there are higher concentrations of negative ions, in order to improve their mental well-being. This is referred to as 'Shinrin-yoku', which means 'Forest air breathing'.
Thanks to NTT Docomo, users can accomplish that effect every time they use their phone.