Use the headset button(s) on your wired headset (as shipped with the N9) or on your wireless Bluetooth headset as shutter button for the camera application. Useful for self- and family-portraits and situations where you want to take a photo with your hands off the N9.
Web page: http://thp.io/2013/headsetcamera/
headsetcamera (1.0.0) harmattan; urgency=low
* Initial release based on an idea by @MikSF