Me personally was never a fan of using condoms for subbing, due to their susceptibility to failure. Mini travel-size shampoo bottles (which are sold unfilled at some major chain retail stores) are far more durable.

As far as checking temp, "stick-on" baby forehead temp strips (sold at most chain pharmacy stores) work wonders. They are identical to the temp strips used by the collection sites and are accurate enough to merit continued use by the collection sites. Just stick the temp strip on your sub bottle, and thats one less item that you have to carry inside the bathroom stall with you (eg; a digital thermometer)