As a follow-on to these questions:
Apple has apparently removed the ability to see other running processes in iOS 9, and throttled (and otherwise limited) the ability to test URL schemes. See: https://developer.apple.com/videos/wwdc/2015/?id=703
What remaining device fingerprinting privacy / security vulnerabilities still exist as of iOS 9, particularly those that have no user controls to block them?
e.g., There have been apps in the app store that show system information like uptime, battery level, disk size and usage, memory size and usage. These could easily be used as elements of a fingerprinting algorithm in a malicious app or in 3rd-party code in an app.
e.g, as always there is basic system info available similar to what any web page can access: IP address, HTTP headers, etc.