"Back to the Future" screen saver and live wallpaper look great on the car head unit screen ,
on your phone or tablet, and even on your Android TV.

How to set your screen saver
Note: Some of these steps may differ slightly depending on the device manufacturer.
Step 1: Choose BTTF Clock as your screen saver
1.Open your phone's Settings app.
2.Tap Display And then Advanced And then Screen saver And then Current screen saver.
3.Tap an option BTTF Clock
Step 2: Manage when your screen saver shows
While charging, docked or both:
1.While on the screen saver settings, tap When to start. If you don't see "When to start," tap More And then When to start.
2.Tap While docked, While charging, or While charging or docked.
Docked means that your phone is connected to a dock, a type of phone accessory.
Step 3: Test your screen saver
To see what your screen saver will look like, tap Start now.
If you don't see "Start now," tap More And then Start now.
Choose when your screen times out
After you've set your screen saver, you'll see it when your phone screen times out.
To change how long it takes for your phone to time out:
1.Open your phone's Settings app.
2.Tap Display And then Advanced And then Screen timeout.
3.Choose an option.
Turn your screen saver off
1.Open your phone's Settings app.
2.Tap Display And then Advanced And then Screen saver.
3.Tap When to start And then Never. If you don't see "When to start," turn off Screen saver.

Note that the system won't start the daydream if you're display is kept awake! Make sure to disable the "Keep awake while charging" option in the Android developer settings (if you have enabled that before). On Samsung devices, make sure to disable the "keep display on while eye contact is detected" option (or how they call that)