A Steam Deck devotee was so fed up with their family borrowing their handheld and leaving it with a flat battery that they have resorted to quite extreme measures. On the Steam Deck subreddit, ConroyyJenkinss says that they have modded the console with a range of anti-sharing measures, including a 3D-modeled spiky case and a taser, among other things.
I Built a Security System for My Steam Deck from r/SteamDeck