Kemico, based on your answer to the OP I gotta ask if you're in hgh school? "Probably be out of the range they're looking for?" If done properly, a sample will remain at body temp indefinitely even without heat pads. It shouldn't be a race against the clock till the temp goes to low and an alarm sounds from your pants.

I would add to Burnt Toast's post by saying that if you had some experience under your belt, you could do it without a thermometer or heat pads but as a first time, you need the thermometer at least and then if you can't do it then yes you will need the heat pads. The goal isn't to slow heat loss down but to maintain the temp at 90-100.