Temperature sensing and microphones are literally dirt cheap. Moisture sensing is a bit harder. Are there any off the shelf solutions that recharge using solar, sense temperature, and can attach themselves to your WiFi? Even better: Any that use Cellular networking?
Doesn't seem like the rotary phone case will protect it very much from the environment (water around it carefully, I suppose, but what if you get a downpour?) Not sure what you can do if the temperature is the problem you're notified about, either...