Blackmagic Hyperdeck Recorder?
As long as your audio is coming over HDMI/SDI with your video stream there is nothing you have to do to record audio aswell. If audio is coming in separately you will want to use an HDMI audio injector or a more expensive SDI audio injector depending on what you use.

And no, there is nothing holding you back of using the hardware in the way you intend to. Though with every new hardware you take to live events, do a dry run before actually using it live and before driving to the event, or you can end up with a nasty surprise.