When I need to know if a pan is above or below 100 Celsius but don't have a thermometer handy, I squirt some water on it. Say I want to check for another temperature, e.g. for the Maillard reaction or killing Trichinella parasites.  What are some ways for estimating other specific temperatures? How accurate are they? 
On the Splenda website it says that Splenda doesn't caramelize like sugar. Admittedly, it is talking about getting the golden brown colour in your baked goods, but I suspect since it doesn't happen in that instance, it wouldn't work in a hard candy.  