If you own one, the app will let you stream Slacker radio stations on-the-go (whether your phone is connected to a wireless network or not).
According to a press release: "Slacker station caching, an exclusive feature for BlackBerry smartphones, enables mobile listeners to store favorite stations on a memory card, allowing Slacker music service to play without a network connection..."
Slacker offers thousands of stations, some programmed by pros, others programmed by individual Slacker users.
The Slacker Personal Radio Mobile can be downloaded at www.slacker.com/blackberry. (Available to U.S. customers, requires Device Software version 4.3 and higher.)