Hmmm, i have a liquid crystal (i think?) one. It's just a flexible plastic strip which changes colour when warm. It's called a feverscan. You put it against bubs forehead and the little boxes change colour to tell you how hot they are (green if the temp is ok, amber if it's borderline, red if they have a fever). It's in Celsius, and it's not accurate within degrees C (like either the whole 39degrees box changes or it doesn't, it can't say they're 39.5 or 38.6 or whatever), but it's close enough to know when bubs is warm, when hot, and when to call the paramedics...

It was very cheap and you can use it with one hand so bubs can be cuddled (held still if wriggly) and no danger of it breaking etc.

B