Among the little fixes and new features introduced last night in iOS 4.1 Beta 1, some 9to5mac readers noticed a very important one: full Bluetooth playback control support for AVRCP-compatible devices.
AVRCP is a technology that allows Bluetooth handsets and car dashboards to take full control over the music playback of another device. Before iOS 4.1, an iPhone paired via Bluetooth only allowed volume control. Now it seems like you can play, pause, skip, forward and back.
Nice addition.