I don't think Ring has quite defined anything specific for the inputs yet (the LM2 has two of them). At some point in the future I can assume they will be used for various things like a cam input for chuff synch on steam locos, or perhaps automatic flange squeal when a locomotive's trucks trip a sensor as they swing out. That's all conjecture at this point, but it seems like Ring built in the inputs in view of future possibilities.
-Kevin