What are the 列表 of things 你 can do with a stop-watch? 哈哈

In season 1, episode 8, "They keep killing Suzie", at the end of the episode Ianto 说 "There's a lot of things 你 can do with a stop-watch.", probably sexual things because of the looks he and Jack shared.
I was just wondering exactly WHAT can 你 do with a stop-watch. Even my sick mind couldn't figure THAT out.
Do 你 have any idea? XD