We’ve been using the Blackmagic ATEM 1M/E mixer switcher to stream events and to use in our own multi camera productions. The ATEM allows you to cut between 8 sources (4 HDMI and 4 HD-SDI). You would normally control the system through a laptop or desktop computer running the Blackmagic ATEM Software Control app. Now a company in the UK is about to make our lives easier. http://www.gallery.co.uk is soon bring an iPad interface for the Blackmagic ATEM line of mixer switchers, including Televison Studio, 1M/E and 2M/E.
Coming soon to the iTunes app store. Imagine being able to switch multiple cameras/sources from one simple wireless device. To see an example, here is a video that we cut in real-time using two cameras and 3 computer screens as sources (the ATEM 1M/E has a total of 8 Inputs).