A couple of months ago, Sena released its Prism actioncam. Among other things, it allows users to add their own narration to footage as it's being recorded, via Bluetooth. Given that the GoPro Hero is still the actioncam of choice, however, Sena has now announced its Bluetooth Audio Pack, that lets users of that camera do the same thing.
The Pack attaches to the back of a GoPro Hero3 or Hero3+, much like GoPro's own LCD, Wi-Fi and extra battery modules. It then picks up the audio signal from any paired Bluetooth-enabled microphone (such as those used in Sena's motorcycle helmet intercoms), and records it onto the video. This lets users add a live narration to what they're recording, or capture their conversations with other linked intercom-users.
The Sena Bluetooth Audio Pack has a range of 100 meters (110 yards), and can be purchased now for US$99. A waterproof case designed to fit the camera and the Pack is available separately.