Most disk-space tools either nag from the menu bar or assume you’re standing in front of the Mac when storage runs out. Mister Plimsoll is built for the case where you aren’t — set thresholds per volume (startup disk, backup drive, external scratch) and route the alert to on-screen, email, or iMessage. Free beta, no account, no tracking, no upsell. Glenn Fleishman is the author.