Apparently these really are a hit in Japan. And it's developed by some Japanese guy.
An unverified Engadget commenter describes the ringtone as follows:
Who would have thought shredding guitar listened through a glass of mudd would have made my wifes breasts so full and voluptious...
The link to which you can download said ringtone has been removed though. But at least you get a rough description of what it sounds like.
I imagine the ringtone to sound so emotionally powerful that our female brethren (lol) grab their boobs in passion and pull upwards thus resulting in larger boobs.
Or maybe saggier flappy boobs. Maybe the 'enlargement' that they speak of is merely relative. D: