So you would like to add heat vision to your DIY projects? The Adafruit AMG8833 Grid-EYE Breakout has you covered. It is a sensor with an 8×8 array of IR thermal sensors that connects to your Raspberry Pi to offer IR temperature readings over I2C. It measures temperatures from 0 to 80C with an accuracy of about 2.5°C.
The sensor can detect a human from a distance of 7 meters. If you know your Python, you can develop custom solutions for this. More info is available here.