I saw this in a recent Sunday flyer and thought this would be a great tool to have when heating sparge/mash water. Better than mucking with my digital thermometer. Just point and shoot!
I have something similar, but I've never used it to measure temperatures of liquids. I would think that steam/vapor coming off the water would skew the results. Also since it only measures the temperature of the surface, I wouldn't use it to check your mash temp.