Here's a company that has not only created software for you to create your own Ringtones out of MP3's, Wav's, etc. but, they have also created an online store so you can host and sell your ringtones.
This is a great solution for future clients who want to create and offering tones to consumers. Agencies/consultants could create the ringtone here and then create an online store that would allow the consumer to call a number and download the tone to the phone. This will eliminate brands having to build all the expensive telephone network and allow it all to be customized rather than simply partnering with one of the large service providers.