Ambitious!
None AFAIK.
But let's go for something like a Mega or so as a starting point. Although you could get there with a mere old-style Nano if you had to.
Yes.
By determining what you need to display on it and under which conditions you need to read/see it.
Shall we start with a couple of months or so?
Of course it is. You do realize you're looking at two microcontrollers (Arduinos) connecting remotely, are you?
Look for something like NRF24L01 modules, but there are a few ways of making this work. The NRF24xxx are popular though.
If I can make a suggestion: work in a modular fashion.
- Create a system that plays pre-recorded sounds
- Create a setup that measures temperature with the sensor of your choice
- Create a setup where you have two arduino boards 'talking' to each other
Then start integrating it all. PS: 3 will be a challenging one; most people struggle a lot with it.