Forget condoms. They are susceptible to leaks and breakage. Stick with bottles.

A digital thermometer is not really necessary. Instead, use the stick on-type baby forehead temp strips (sold at most chain pharmacy stores). They are similar to the temp strips used by the collectors at the facility. While they may not be as accurate to the "nth" degree as the digital units, they are obviously accurate enough to merit continued use by the facilities.

Just stick a temp strip on the bottle and thats one less item that you have to sneak into the facility.