Connectors Likely Found Inside a Retro Module
Consider, as you make, what devices you have which can be easily adapted to the Retro Specification. One or more off-the-shelf devices may comprise a single Retro Module. In this context, off-the-shelf device connections can be considered "internal".
Have an old composite video screen and a GoPro? Make them both into Retro Modules. Separately, make a pair of wireless AV Retro Modules (research 'FPV'). Once complete, you would have a wired/wireless GoPro video setup which can be assembled in seconds.
Any combination of devices can be considered a module. Large devices, like a car -- or a satellite -- can be considered modules. Each feature various popular "internal" connections (OBD, M-Bus, USB Audio, etc.). An existing module can be made into a Retro Module by exposing these "internal" connections on a Retro Module connector.