System Status Pro
Proven Hardware Monitor
Developed by: Techet
Date of purchase: 27.03.2016 for 2.99 EUR
Rating: ***** 5 stars
Compatibility: Requires iOS 11.0 or later. Compatible with iPhone, iPad and iPod touch
Functionality: with such an app you can display the technical data of your device, some of which Apple likes to keep quiet about (e.g. the battery capacity).
In addition, you can check much kinds of operating states, e.g. whether a newly installed app is keeping the CPU busy and how much memory it is using. More interesting is certainly the consumption of data volume with WiFi and mobile networks.
If your iPhone/iPad/iPod touch does not function normally, you can quickly find out whether the processor is busy or the memory is full. Unfortunately Apple has blocked access to some interfaces (API's), so that you can no longer display the temperature of the CPU or battery, for example. The developer of this app is not responsible for this!
So if you only wanted to buy this app to display the temperature of CPU or battery, you should postpone the purchase for now.
It does not look like Apple will ever make such data transparent again. Maybe a new CEO will think differently? On my iPhone 6s Plus the temperature display 2016 was possible for a short time.
I had mentioned it in a test of the iPhone 6s+ and therefore I could now look it up very fast: With iOS version 9.3.3 (or only 9.3.4 ?) came this API release for software developers; since then System Status Pro and similar apps could display the battery temperature.
With iOS version 10.0.1, this API was removed. Incomprehensible and a pity!
Conclusion: highly recommended
Even without temperature display, this hardware monitor offers enough measurement data for nerds, geeks and other technically interested people.
If you have an Apple Mac/MacBook/iMac, you can access the Lightning socket of the iPhone with suitable hardware monitor software for macOS.
iMazing, software for managing iOS devices on Mac and PC can also name some battery data including temperature.
However, there is a special Hardware Monitor software for macOS which can read operating states via the Lightning interface. I had read about it years ago, but forgot the name. I will deliver it ASAP. Maybe you know it?