Battery Graph Widget
Battery Graph Widget tracks the battery level of your device and displays the graph with battery level. Furthermore, it calculates the estimate when the battery will be empty based on your past usage.
The graph and estimates are displayed in the Today view as well as in the app. You will need to add the graph to Today widget with a few simple steps.
Both the graph in the app and in the Today widget are customisable. You can select the colour of the graph, whether it is filled with a gradient and whether the grid lines are displayed.
References
10 of the best iPhone widgets in the world @ BGR (#3)
12 Essential iOS Widgets For a More Functional Notification Center @ Gizmodo (#6)
25 Best iOS Widgets That You Need Always On iPhone & iPad @ GoToWebsites
Get Android-like Battery Graph iOS Widget @ Cupertino Times
How To Get A Detailed Battery Graph Widget In iOS 8 @ Redmond Pie
and many more...