Sir,
I actually just completed a couple of designs that had a 2x8 LCD alpha numeric display for the temperature reading in C, and included a sub board that had 4 switches for setting the temperature thresholds, etc. Of course its all programmable as well, so the buttons can do anything you need them to do. One design used a TMP102 temperature sensor on the board, and the other, a more expensive solution had a SHT11 sensor for both temperature and humidity. I believe I have some boards left over from the project that could serve as a prototype and then redesigned if necessary for your own purposes. The processor is a PIC 18F23K20, and runs from two AA batteries with the necessary boost circuits on board. The firmware will have to be written for your specific requirements and adding the LEDs as well but this can be discussed further if your interested. You can see some of my products at www.pic-bee.com.