Locational service notification I would like to know if there is any app that would notify me when locational service is being used up . Or it been open . 

My ex wife has my find my iphone . I get a little arrow when she is using it . But it doesn’t pop up notify me when it’s been used .
No - apps don't get to track other apps and their use of the location API. This is by design of sandboxing, entitlements and public SDK/API and the review process to catch apps using private API.

You need to use Apple's iOS features to verify which apps use location and trust that is correct. 

The overview of privacy and location services is: 


https://support.apple.com/en-us/HT203033 - About privacy and Location Services in iOS 8 and later
https://support.apple.com/en-us/HT207056 - About Location Services and Privacy


Each fall, these articles above usually get updates due to the new OS. In the spring, a formally written and reviewed (Apple brings in consultants to audit their code) and then publicly documents formal design decisions) in a white paper. The one for iOS 10 from March 2017 is available.