Sirius XM Radio (Nasdaq: SIRI) is making the most of its new deal with Howard Stern. After months of public quibbling with its most magnetic celebrity, Sirius XM signed Stern for five more years back in December. It's already paying dividends.

Stern was on Comedy Central's popular The Daily Show with Jon Stewart last night, working his ambassadorial magic, promoting his show's availability since January on smartphone apps.

"You can listen to us on your cell phone now," Stern told Stewart. "It's almost like the transistor radio has been invented."

Sirius XM pushed hard for smartphone streaming applications nearly two years ago. Rolling out apps for owners of Apple, Research In Motion, and Google smartphones seemed like a good idea, but the initiatives have failed to publicly move the needle.

Maybe it's the gamut of aural options on Web-streaming gadgetry for those considering stand-alone online subscriptions. Maybe it's that commuters who already have satellite receivers in their cars don't spend enough time listening to their cell phones to justify the cheaper add-on smartphone subscriptions. However, those who originally balked because Stern wasn't available through Sirius Internet Radio no longer have an excuse.

Plugging Sirius XM as a streaming product wasn't Stern's only promotional win last night. He also found a way to thrust himself into the Charlie Sheen media frenzy. His producer apparently got a hold of Sheen earlier this week, urging him to appear on Stern's show because both Stern and Sheen had their legal run-ins with CBS.

Stern suggested to Stewart that Sheen might call in to his radio show this morning. It wasn't an empty tease. Sheen was a guest on Stern's show today. "They're soft targets in cheap suits," Sheen said of his CBS adversaries during his appearance. It's one of the many quotes this morning that are bound to make the media rounds in the coming days, once again promoting Sirius XM.

It's good to have Stern!

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Longtime Fool contributor Rick Munarriz is a subscriber to both Sirius and XM. He does not own shares in any of the stocks in this article. He is also a member of the Rule Breakers analytical team, seeking out the next great growth stock early in its defiance. The Fool has a disclosure policy.