As I slide my finger into the hand grip, a rubber ring clamps down on my knuckle to hold it into place. It’s a gentle reminder that I should be moving as little as possible... as I watch the tiny brush head trace an almost-perfect outline of my nail before continuing to fill it in with color in a mesmerizing loop, I reluctantly admit to myself that this is, almost certainly, the future. For starters, a robot painting your nails is fast and cheap. The shellacking of a deep maroon cost me $8 and was done within 10 minutes. Plus,...