I know you mentioned underarm or rectal but I wanted to recommend the temporal thermometer. After two years of struggling with several types of thermometers, my second child came along and seemed to constantly have a fever. Again the struggle continued trying to get an accurate reading using everything from underarm, ear, to paci kind. My neighbor had the temporal kind and I was constantly borrowing it. I decided we needed to go ahead and get one...I asked for one for Christmas...best gift the girls ever received :) Very fast, accurate and no crying or struggle!!! They are around $40 at Walmart but well worth it....wish I would have just purchased it from the beginning rather than spending $10-$20 on all the other different ones.