iOS - Receive an external input to my app from a switch with BT or IR?

Question

I am building an assistive iOS app for a kid that uses a switch to control his computer (a simple button that can send only one massege to the computer).

I am looking for a way to connect my app to a switch that can send click events to my app. It can through by BT, IR or even through the earphone connection (headset port).

(BTW he can not use the iOS screen as the switch).

Any ideas ?