How do you create a transparent demo screen for an Android app?

Put your demo info in a different activity and give it the following theme.

<style name="Transparent" parent="@android:style/Theme.NoTitleBar">
    <item name="android:windowContentOverlay">@null</item>
    <item name="android:windowIsTranslucent">true</item>
    <item name="android:windowBackground">@android:color/transparent</item>
    <item name="android:windowNoTitle">true</item>      
    <item name="android:backgroundDimEnabled">false</item>
</style>

If you're using ActionBarSherlock change parent to @style/Theme.Sherlock.

This will give you a transparent activity, so you will be able to see the activity below it.

Now I'm guessing you want a translucent background too.

In the xml layout (of your transparent activity) add:

android:background="#aa000000" 

The last 6 digits define the color: 000000 is black.

The first 2 define the opacity: 00 is 100% transparent, ff is 100% opaque. So choose something in between.

Have you looked at ShowcaseView? https://github.com/Espiandev/ShowcaseView.

Using this:

View showcasedView = findViewById(R.id.view_to_showcase);
ViewTarget target = new ViewTarget(showcasedView);
ShowcaseView.insertShowcaseView(target, this, R.string.showcase_title, R.string.showcase_details);