Android P will get quite an interesting functionality, thanks to which you will learn if someone was recording a phone conversation in which you participated.

Android P will be the next version of the system that will appear this year. Yesterday I mentioned that we should expect her to include significant changes in design. Android P will adapt to different displays – those with screen cutouts, foldable or double screen. For sure we can also count on extending the device's operating time on the battery. However, this is not the end of changes that flow to the surface. Soon we will learn much more, and an example may be the latest report. The Android 9.0 P has built-in support for warning sound , which will appear when a phone call is being recorded by someone else. On the XDA website we will find an explanation of the operation of this functionality. The name of the application package recording the connection will be detected, followed by the insertion of the 1400 Hz tone. The sound will appear every 15 seconds. Unfortunately, this option will only be available if the mobile operator we use will enable this option. Perhaps the discussed whole will be more widely available at a later time, when it will become more popular. Source: XDA