Apple - How to determine iOS app usage frequency for iPhone or iPad

I think I may have found an astoundingly low-tech solution to this problem, and it was right under my nose.

Ever since iOS became "multi-tasking" capable (I say that tongue-in-cheek, as we all know that most apps that get backgrounded aren't still running, they've just had their state saved until used again), the Task Switcher, accessible via a double-press of the Home Button, shows you a more-or-less "use-ordered" list of your apps. Unless you deliberately open the Task Switcher and kill the apps, they linger in there... I guess forever, or until you reboot the device.

So, if I clear all those out, and then just go about my business using my device for a while, and occasionally look at what apps are in my first 3 or 4 "pages" in the Task Switcher, that gives me a decent idea of which apps I use the most-- or at least can tell me the ones that I've used "most recently". Those apps that are on the far right "page" of Task Switcher are the least used (or at least the ones that were used "least recently").

EDIT: As of iOS9, the order of applications displayed in the Task Switcher is reversed. The most recently foregrounded app is on the far right.

I suppose a person could extend this into a true exercise in statistical geekery by noting the order of the apps on a schedule... say every morning or every evening (or more or less often)... over a period of time; a week, a month, whatever. Then you could compile that into useful info for yourself.

I'm sure people have probably realized now how to get around-about-answer on this subject but I have been searching for an answer for an hour and figured out a way to kind of get an answer. If you have iOS 8 (now that this post is years after the original question..)

Settings > General > Usage > Battery Usage

And you can see which apps have used the most battery power in the last 24 hours, and also in the last 7 days. Which answered my question! Hope this helps someone.

This is available in IOS 9.2

Just discovered after reading this list that if you do as previously suggested

Settings > General > Usage > Battery Usage

and tap within the list. Then each entry will display hours of on screen use and hours of background use, as well as the overall percentage. It works within the 24 hours view and the Last 7 Days view.