I've read many articles recently that make similar claims. Chapter 10 of NurtureShock talks about this. Anecdotally, the idea seems to be growing in popularity idea among my fellow parents.
One way to capitalize on this would be to create a mobile app which functions like a pedometer, except it counts the number of words you speak to your child. Parents could talk to their kids during playtime, and the device would listen in and use natural language processing to interpret the conversation. Parents would later get a report on the frequency, complexity, and novelty of the words used. They could chart progress over time.
As I read your comment I was afraid you were going to suggest an app that speaks to your child for you, but I was pleasantly surprised. I like the idea.
One way to capitalize on this would be to create a mobile app which functions like a pedometer, except it counts the number of words you speak to your child. Parents could talk to their kids during playtime, and the device would listen in and use natural language processing to interpret the conversation. Parents would later get a report on the frequency, complexity, and novelty of the words used. They could chart progress over time.