There are multiple ways to unpair Broadcasters from your account. For all devices, go to your account settings, then navigate to the 'Devices' tab.
Click the 'Unpair' button that corresponds to the device you wish to take off of your account.
You can also do this in the Livestream mobile app. Go to Settings > Livestream Broadcaster.
On the device you wish to unpair, use your finger to swipe from the right to the left. You will see Reset as an option. This will both reset the device and unpair it from your account.
The Broadcaster and Broadcaster Pro can also be unpaired directly from the device. Navigate to Menu > Account > Unpair.
All options will reboot the Broadcaster, eventually giving you the option to pair again.