It was refreshing to crack open the Best Buy (NYSE:BBY) circular over the weekend and see Sirius XM Radio's (NASDAQ:SIRI) new XM SkyDock prominently featured.

Satellite radio receivers are occasionally advertised at the consumer electronics superstore, but it almost seems like an afterthought. The numbers bear out that assumption. As a platform, satellite radio has been fading in popularity at the retail level for quite some time. Its real growth has come from sales of new cars with factory-installed Sirius or XM receivers.

So all things considered, I was more encouraged by yesterday's bullish report out of Ford (NYSE:F) than by Sirius XM's press release signaling the SkyDock's nationwide availability.

Is it cool that this thing is now being sold at Apple (NASDAQ:AAPL) stores? Yes. You've scored some serious validation points once you work your way into suburban malls' tastemaker chain.

However, I wasn't sold on the SkyDock when it was first unveiled three months ago, and I'm still not changing my tune.

I think it's great that this device uses an iPhone or an iPod touch as a high-end display unit. I can't badmouth the ability for owners to tag songs they hear for purchase through iTunes later. The thing even charges the iPhone, so it's not as if it's a battery hog.

But I'm still betting that the SkyDock doesn't move the needle for Sirius XM. Satellite radio is awesome, but Sirius XM is aiming at a tough crowd here.

iPhone jockeys already pay $20 to $30 extra a month for their unlimited data plans. The smartphones also double as iPods, so music lovers already have them loaded up with tunes of their choosing. Between free Internet radio and digitally-downloaded songs and podcasts, is there really a market here for consumers to pay $13 more for a SkyDock subscription they can only enjoy in the car?

It's true that Apple and AT&T (NYSE:T) are meanies when it comes to accessing free Web radio over anything but a stationary Wi-Fi network. That will change the moment that AT&T lives up to the "unlimited" in its data plans, the way it has relented in letting Vonage (NASDAQ:VG) and other telephony apps lean on its 3G network for voice chat.

We'll see.

Thursday's conference call will be too early to get a read on SkyDock orders, but the company will finally have a full quarter of Sirius XM's premium app through Apple's App Store to discuss. If the numbers are immaterial, it will be hard to get excited about winning over the Apple crowd with a car-docking station for satellite radio.

Best Buy is a Motley Fool Inside Value recommendation. Apple and Best Buy are Motley Fool Stock Advisor recommendations. The Fool owns shares of Best Buy. Try any of our Foolish newsletter services, free for 30 days.

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