An Android app that adds a layer of transparency in front of your applications, so you keep an eye on what is happening in front of you while looking at your phone.
Yes, it is free. It may show ads provided by Google AdMob (see the privacy policy).
Launch the application to activate Transparent Mode. It is not just a wallpaper.
Shake your phone. The level goes from 1 (opaque) to 5 (translucent). The default level is 2.
On the Transparent Mode privacy policy page.