We’ve seen Parallax PING projects for sensing water depth and to generate music. These could be hacked to use the HC-SR04 using [Clint’s] techniques. [Arduino and HC-SR04 photo from Blax Lab ] ...

Sharp Develops 3D Touchscreen LCD—Switchable Between 2D and 3D Modes—with Industry's Highest Brightness*1 Enables 3D Images Without the Need for Special Glasses ...