Actually, you have to do your part, too. But the OV-Watch--FDA approved!--monitors the salts in a woman's sweat to predict the six days when she's most fertile. Now, isn't that romantic? (It would be more so, we think, if this watch came in any color that didn't scream, "Look! I'm trying to make a baby! And I love princesses!") Be prepared to shell out $100-plus for the watch and sensors to go with it.
(Via Babygadget, Photo: OV-Watch)