Adafruit Contact-less Infrared Thermopile Sensor Breakout - TMP007 [ADA2023]

As a general temperature sensor, this works really well.If a precise measurement is required, then it is best to perform an accurate calibration, since the reading can easily be off by a couple of degrees: this is not necessarily indication of sensor's fault, rather it is due to the way the reading is performed.Being a contact-less sensor, the reading can be affected by material, angle of view, distance, etc.I still think it is a good product, worth its price.

Temperature can be way out, and needs equipment to calibrate properly to the material you are measuring. Works well enough for some applications though.