If u could invent one science gizmo what would it be?

A simulation. A game where anybody could log in at anytime and put on a VR headset and in the game you would be able to hear, talk, sing, dance, taste, and touch anything and everything in the game. the game would allow you to see any place in the world. The game would also allow you to meet other players and go to school with them and play other dames inside the game like PacMan.

(Inspired by the book Ready Player One, its a very good book)

that wouldn't exactly do anything. if people have no idea what app you're using and also don't really care, then they won't/can't do anything against them.