You can use NRQL to query the application data collected by New Relic APM, New Relic Browser, and New Relic Mobile. You can then use this data to answer a variety of questions. Here are some basic examples.
How many unique user sessions did you have in the last week?
Were your unique user sessions up or down last week compared to the week before?
How can I graph the number of unique users yesterday compared to the day before?
How many of your mobile users are on the latest OS version?
What is the Apdex score for a particularly important customer? If you have defined some custom attributes, you can query to monitor how this customer experiences your app from a performance standpoint: