Ever since Slacker Radio decided to flee the hardware business, we've been looking forward to bigger and better things from its mobile apps. If the hands-on that Dave Zatz got with the version 2.0 software for iPhone is any indication we won't be waiting in vain, either. The big news here is station caching: that's right, users will soon be able to store music for off-line access, whether you're listening on a plane or in a dead zone. Exactly how many stations (and for how long) you can store is currently a mystery, although the reviewer said it took about 20 minutes to cache six stations, with each one being good for at least a couple hours playback. In order to take advantage of this, you will need to purchase the Slacker Radio Plus package, and you'll have to wait for the app to be approved by Apple, which could be a couple days from now -- or it could be never, depending on Apple's mood.