I'm looking into Apple Docs but I can't find anything I need.
I need to create an external hardware button connected to the phone with the lighting port. Whenever I press the button, the phone will launch a phone call to a number saved on the memory of the external hardware. Is it possible or not?
Thank you very much.
Check out the documentation for ExternalAccessory . Everything you need/possible is documented there basically.
Edit: As commented below:
Be aware that you need to apply and get approved for a special developer program in order to be able to create external accessories. – Duncan C 7 secs ago