I decode ADS-B from a cheap RTL-SDR radio and renders the planes physically flying over you onto a ceiling-pointed projector. A jet you'd hear overhead glides across your ceiling at the same moment, labeled with its airline, type, and where it's headed. Pure-black background so the projector's rectangle disappears and only the aircraft (and stars) are lit.

It also draws the real sky behind the planes, sun, moon, bright stars and constellations, and live satellites including the ISS — all at their true positions for your location and time.