The Echo Master app creates a small file on your device to keep track of these three things:
Those three things are stored in a small text file on your device (I don't actually know where specifically), which is deleted when you uninstall the app.
Neither this file nor any other information is ever sent to me by the Echo Master app.
The app can only be acquired via storefronts operated by Google and Apple, however, which means you may be interested in reading their privacy policies:
This page was written by Graham Hamilton, and was last updated on October 31, 2020.