Trew made me a custom box that plugs into my 788t headphone jack. I then plug my headphones into it and the return signal from the camera. That allows me to select direct 788t or return sound. It has a volume control and a left/right/stereo selector.
It cost $110.
I also had them wire a custom break away cable with timecode built in. I had the time code Lemo to Lemo w/ adapters on the camera side (Lemo to Coax in & out).
It should also come in handy with the 552 when it comes out.