wireless temperature, humidity and gas sensor with cloud connection

I am hoping to build several small wireless sensors which measure

  1. temperature
  2. relative humidity
  3. air CO2 concentration
  4. air alcohol concentration

and which connect to a cloud service for data visualization and logging.

I have been able to find projects which are close to what I need (linked below), but I am hoping to fill the following criteria:

a) miniaturization (eventually I'd like to get it the size of a lighter or something thereabouts).
b) low power (I'm hoping it will run for months on a small battery). It will be measuring data in a very small enclosure (less than a liter of air) and so it shouldn't affect the temperature too much in there.
c) low cost (ideally it would eventually be around 15USD or so, but initially I don't mind having something more expensive.

I thought I should ask here in case people have an idea what the best current tech would be to use.

Q0) I imagine someone already did this exact project already, if so let me know.
Q1) Should I use bluetooth for this, or are the wifi modules low energy enough to be used long term like this?
Q2) Should I use sensor packs like the TI Sensortag?
Q3) Should I miniaturize by using ATtiny?
Q4) What cloud data service would be best if there were say 10 of these sensors?

https://openhomeautomation.net/arduino-bluetooth

CO2 and alcohol sensors usually have power hungry heaters, and need to be wall powered for long term continuous operation. The good ones are not cheap.

There are many commercial wireless sensors that report temperature and humidity and run for a couple of years on an AA cell. Many have been hacked and can be read by Arduino, so no need to reinvent the wheel for those cases.

jremington:
CO2 and alcohol sensors usually have power hungry heaters, and need to be wall powered for long term continuous operation. The good ones are not cheap.

There are many commercial wireless sensors that report temperature and humidity and run for a couple of years on an AA cell. Many have been hacked and can be read by Arduino, so no need to reinvent the wheel for those cases.

Thanks for this, I will have to change my design idea. I'll have to do a single dedicated sensor chamber for the CO2 and alcohol. Thanks.