It is not all that difficult.
You can use Thingspeak.com to receive your readings, and then set a condition in ThingSpeak that will trigger an action if the condition is met. So for example, I have an event that sends me a text via Twilio.com if the temperature is outside a certain range.
Go step by step.
a) Get the Photon to work with your chosen temperature sensor and display the results locally to the serial port. Get that working 100% to your satisfaction.
b) Start publishing to ThingSpeak. Make sure that works 100%.
c) Set up the connection between ThingSpeak and Twilio.
I just finished a sensor network that shows me the data from 9 (or more) different sensors (anywhere in the world), plus the local weather forecasts for today and tomorrow, all on a 1.8" LCD hooked up to a Photon.
It is not difficult, and it is a great learning experience.