Q: program to monitor time spent on an Ap monthly

Looking at my 10 pages of aps I have on my Iphone 5s 16GB  (latest 9.0.2 ) and remaining size of memory is down to 1.5Gb .  Have looked at all my aps and can't quite narrow it down to:

"we know who stays  .. But WHO  Goes ????

Have I overlooked a shortcut  designed for me to monitor this thru settings? ..?

or has it not occurred to the programmers to add such a timer ?

should be easy to do as all of our network time is captured and each of those captures is shown a site that might have been approved by a certain  AP..

there fore attach these saved / along with ID 'd codes to a calculator and voila ..

Looks like I never use  the Yelp Ap  or one of my three weather aps ...   Gone ..

I'd  Vote for one ..  Is there a site to get this petitioned??