Signal Spy provides you with up-to-date data usage information so you can see how much data you use each day broken down per app. 

 For free users, you can see the apps that used data today, with the amount used, sorted alphabetically by app name. 

For Pro users, you also see the list of apps that have used data and the amount used but in addition, you can sort this list by the amount of data used or by the name of the app. You can also use the calendar to check your data usage on different days or the total data used over several days.