WatchGit was created by Atadore, a Swiss company.
Atadore does not collect or store any data on its servers when you use the app. It uses an Atadore server to facilitate the OAuth login, but stores nothing there once you’ve finished logging in. Nor does the app use third party services for analytics, advertising etc.
This app DOES send your data to GitHub’s servers to provide GitHub functionality. The GitHub privacy statement is here
In brief, this app does not send data to Atadore’s servers, nor to services other than GitHub’s.