The GPI and Tally Interface from Blackmagic Design provides 8 contact closure inputs and 8 contact closure outputs for connecting to ATEM switchers and Videohub routers. Tallies will be displayed when connected to an ATEM switcher to indicate their "on-air" status and you can even connect multiple interfaces together to increase the number of inputs and outputs. GPI and Tally Interface also works as a Videohub control panel without buttons and LEDs so you can make your own! Now anyone can connect to Videohub routers to control cross-points.
Blackmagic Design GPI and Tally Interface Specifications: