Most musicians haven’t taken ringtones very seriously, either as a promotional tool or as a new platform for music.
I think this is a mistake. New phones have all sorts of multimedia capabilities, but their built-in ringtones are usually horrible.
Android is a new phone platform spearheaded by Google. While it’s not as well-known as the iPhone, it looks like it could develop into a strong competitor to the iPhone. If it does, it’s going to be another important platform for musicians to think about.