Now is it bad enough that you let somebody else kick your butts without you trying to do it to each other? Now if we're all talking about the same man, and I think we are... it appears he's got a rather growing collection of our bikes.
I would think of bar code reader, fingerprint readers, readers for magnetic stripe cards and smartcards, ... In the IoT-world you do I/O through sensors, actuators - or, from the other end of the chip: Bluetooth (or other radio protocol).
Buttons hard-wired to the I/O pins of the processor. I'm living in the embedded world now.
But even in the olden C# days were there dedicated PCI(E) I/O cards to have buttons or position indicator switches attached to the PC.
Or they were dangling from a parallel port.
Once even an RTS/CTS signal line had to do the job.