New parents hear the advice often: You need to talk to your baby! A lot! The book SuperBaby proclaims 30,000 words a day is the magic number for optimal language success. One landmark study found that kids who heard 45 million words by age three later scored the highest in reading and maths. There's even a wearable word counter that you can clip onto your infant's onesie and see via an app whether you're meeting your daily word goals. Basically, a verbal Fitbit.