PhoneCell is a popular iOS app for CPU & Memory & Storage Usage tracks the battery level and storage space of your device and display the graph with battery level and storage space you have used.
The graph and the estimates are displayed in the Today View of the Notification Center as well as in the app.
The Widget in the Today View is not displayed by default. You will have to add it with a few simple steps.
Add Cellular and WiFi data usage since the device boot.
Add Memory information of your cellphone.