You could use Pi0W with built-in WiFi, or Pi3B (ditto), but for simple programs and no GUI scotty's suggestion may well be lower cost. A Pi will probably be better if either part requires a GUI (screen, mouse and possibly keyboard).
I don't quite get why you need to signal inputs to a remote computer to work out the outputs and signal them back -- can't it all be done locally?
Or is there more to the remote processing than that, like passing information elsewhere or repeating the display?
Have I missed something? What are you actually trying to achieve?
"If it ain't broke, fix it until it is."
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