If you install this app on any phone, it will secretly transmit all incoming SMS messages to the phone you choose.
This app has no icon, so once it is installed, it is impossible to find on the phone and will run on its own. The only way to reveal the app is to text the phone with your secret password.
This application was removed from Google Play Store, and the developer’s official website seems to be abandoned. You can still find similar APK files for this app from 3rd party sources, but we highly recommend using only apps from trusted sources. (2023 update)
Here are a few snapshots from the app’s user interface.