Stopwatch

A stopwatch was a type of watch used to measure the amount of time between the beginning and end of an event. According to Ianto Jones, there were "many things you can do with a stopwatch." This apparently had sexual implications.

One of the various uses was in conjunction with the resurrection gauntlet: Ianto would keep track of how much time they had left until the victim would die again. (TV: They Keep Killing Suzie)