This excerpt taken from the SIRI 10-K filed Mar 13, 2006.
SIRIUS Via Mobile Phones. In June 2005, we signed an agreement with Sprint to offer select programming over the Nationwide Sprint PCS Network. In September 2005, Sprint began offering a SIRIUS music service to its subscribers through a built-in media player on Sprint PCS VisionSM Multimedia Phones for $6.95 per month, a portion of which we receive. This service includes access to 20 commercial-free SIRIUS music channels, plus a channel devoted to artist interviews and performances. Subscribers to the Sprint service are not included in our subscriber counts.