The Delphi XM Roady XT supplants the Roady2 as the smallest, simplest way to add satellite radio to your car. At 2.4 by 4.0 by 0.7 inches (HWD), the XT is one-quarter smaller than the Roady2 (which is now just $50).

The Roady XT requires minimal setup: Put the tiny antenna on your car's dash or roof, plug in the power, and tune your car radio to one of the 100 frequencies transmitted by the XT's built-in FM modulator. There's even a line-out jack, should you want better sound. The Roady XT has a three-line display that can stream stock quotes and sports scores.

Products such as Roady XT show that the XM side of the satellite radio business has the lead in compact hardware design and that may be a deciding factor for uncommitted users who want mainstream musc – pop, rock, classical, music of the decades – that both Sirius and XM do well.

Even though it's one more thing taking up space in the cockpit, you'll probably find it's so small and unobtrusive that you won't mind. To make it most unobtrusive, we'd recommend having the antenna, power, and line-out connections made permanent and tucked out of the way under the dash.

If you're having it done for you and your car radio doesn't have a line-in jack, see if there's an electronic coupler for your car model that can be connected via the (likely unused) jack for an external CD changer. Barring that, get a hard-wired FM modulator that plugs directly into the radio's antenna jack, which is better than the Roady XT's over-the-airwaves modulator.