At 3.1 ounces, the XMp3 is lighter than the iPod Classic (4.9 ounces) and the iPod touch (4.05 ounces) but obviously doesn't come close to the nano (1.3 ounces). The XMp3 measures 2 inches x 3.6 inches x .6 inches deep. At $279.99, the XM player costs more than the iPod line, but adds a bunch of unique features, too.

But there's a catch: the battery life. The included battery lasts for a rated 16.5 hours of MP3 playback, but only 4 hours of live XM radio.

However, the player also packs a number of nifty features. In addition to the MP3 playback capability (MP3 and WMA formats are supported), up to five XM channels can be recorded simultaneously. In addition, there's a handy DVR-like capability that caches the last 30 minutes of audio you've heard, so you can go back and replay a clip again before it's lost. Moreover, up to 10 hours of individual songs can be downloaded from XM and stored on the device.

It's not clear what the internal capacity of the player is, and whether it's based on flash or an internal hard drive. We've asked Pioneer and XM for comment, and we'll report back once we've heard. EDIT: The XMp3 contains a 2-Gbyte flash drive. MP3 and WMA files can be loaded from the user to the XMp3, according to company information provided by a Sirius spokesman.

Pioneer and XM do say that songs can be stored on the player and managed by the XMp3's internal software. That software also includes a channel guide, with broadcast schedules listed up to a week in advance. TuneSelect also flashes alerts when a selected song or artist is playing.