Thanks for the suggestions. I'll come back to this project when i have more time to work on it.
Hi welcome to the forum,
One of the problems you are facing is that the products you mention might have proprietary protocols. I'm not familiar with them but have seen several 433Mhz device discussions on this forum. So that is the first thing to find out. Do you have datasheets about the signals send?
Connecting an Arduino to a doorbell is relative simple. With the analogRead() one can see if a voltage is LOW or HIGH. You probably need an optocoupler to protect your Arduino, or a rectifier and voltage divider. There are many projects interfacing with doorbells e.g.
In a similar way you can connect to a fire alarm. Measuring the voltage over the main buzzer with Arduino is very well possible.
Unfortunately a project like this is unlikely to be done urgently as there is a lot of work to get it going.
We can help with particular aspects but this is not a quick and simple project.
Weedpharma
I think weedpharma is right. You haven't time to make anything fancy now. So you should probably just try to MacGyver something.
Alarm clock:
Take something, anything that runs on mains power and vibrates enough to wake you up. (A trip to the hardware store might help.) Also buy one of those timers that people use for their lights when they're on vacation. You see where I'm going with this.
Doorbell:
This is the 21st century, so you probably have a cell phone that can vibrate. Keep it on you, and leave a note on your door: "I can't hear the doorbell. Please call my cell phone to be let in." This is only a problem until you let at least one hearing person in.
Smoke alarm:
Sorry, I have no idea.
Anyway, I don't understand why you're going all "wireless" / "app" / 21st century about all this.
Are you sure that a solution with 20th-century technology wouldn't work as well and be easier to put together?