Slacker has released another update to its popular Slacker Radio personalized streaming radio application, adding support for background audio on multitasking-capable iOS 4 devices. With Slacker Radio 2.1, iPhone 4, iPhone 3GS and third-generation iPod touch users can now start a personalized radio station playing and then exit the app while the music continues playing in the background. Slacker Radio 2.1 also builds upon the offline listening feature…
