When a phone rings with an unknown number, we all fear robocallers, scammers and spammers. January 25 is National Opposite Day, a perfect opportunity to turn the scammers into the scammed. RoboKiller is a call management tool that seeks to engage the scammer in a time-wasting, inane conversation with a realistic recorded voice. RoboKiller answers the call for you and starts responding with a colorful collection of crazy conversations. Other robocall services worth mentioning are YouMail, Hiya and Nomorobo.