looking for doorbell-intercom system that works with the iPhone

I'm looking for a an intercom-doorbell system tworks with the iPhone and is accessible. I can't always hear who is on the other sid
of the door. I am totally blind and partially deaf. I use VoiceOver and a Focus 14 blue 5th genery braille dispay . I am running the latest version of IOS. Where can I find one of these systems and how much? How do I us
one?