Google has introduced a new way for developers of apps that have Google Cast functionality to better understand how people are interacting with their apps. Developers will be able to see how many Cast devices have connected to your app, how long the average length of use is and much more. Interested developers are able to log into their developer console, and in the "Application" table just click the view link in the "Statistics" column. From Google's Developer Blog:

The analytics page contains a tab for each metric, an interactive graph of the metric's values over time, and tables containing the most recent day's data. The devices tab shows the number of Cast devices that have launched your application, the sessions tab shows the number of Cast sessions of your application, and the average playback tab shows the average length of media playback time per session for your application.

This information can be very helpful for developers to gain a better understanding of how users interact with features of their apps, and hopefully make changes and improvements to increase the functionality of their apps.