If you're running Switcher Studio on an iPad, you can use a bluetooth keyboard to switch between your connected camera angles. It's not currently possible to use a bluetooth keyboard to start and stop the production.
Here's how to set up and use a bluetooth keyboard with Switcher:
Connect your bluetooth keyboard to your iPad.
Open the Switcher Studio mobile app on your iPad.
Connect additional iOS devices as cameras, like normal.
You will notice that the cameras are all labeled 1, 2, 3, 4, etc. This is important, as it correlates to the number keys on your keyboard.
Tap a number on the keyboard to switch to that respective camera source.
If you're using the Preview Window, you can adjust the camera in the preview window as normal and hit "Preview->Live" to go Live.
Note: Using a bluetooth keyboard requires an iPad as the main switcher. If you're using an iPhone or iPod Touch as your main switcher, you cannot use a bluetooth keyboard to control your cameras.