Is it possible for an Android app to modify the screen at all times?
<p>To give a ridiculous example, could you have a water app/service that stayed on the display AT ALL TIMES (or perhaps only when not actively using another application) and caused ripples to occur when you touched the screen? I would not want an app like this, but it's just an example.</p>

<p>I know there is a live wallpaper for this, but it is in the background. What if you wanted the affect on top of your icons and widgets and UI as well?</p>

<p>Is this possible?</p>
