One of the coolest ideas in the MC (referee) advice section of Apocalypse World is the countdown clock. Essentially, a countdown clock is a handy way to represent dynamic threats in a campaign world. Modeled after the Doomsday Clock, it looks like this:
As a software engineer, I look a countdown clock (or a collection of countdown clocks) and see a simple kind of state machine ("if X happens then we've moved stage Y", "if we're in stage Y then Z happens").
You could also look at like a wound chart for a world's status quo. The first three wound "boxes" represent relatively minor changes to the campaign setting that can be mitigated or even reversed fairly easily. At 9:00, however, a death spiritual is initiated and things are likely to accelerate to 12:00 and the ultimate manifestation of a given threat.
Countdown clocks are a great way to interject a form of plot into a sandbox setting. The wold is alive and NPCs and threats are always in motion. A handful of countdown clocks would be a great way to keep track of these threats even as the characters only tenuously interact with them.
I'm also enamored of the simple economy and limited scope of the clocks. Limiting things to six states seems like a great way to reduce complexity, limit over-planning, and keep focus on the events that matter.
Alas, I was unable to really make use of countdown clocks during my last session of Knights of the Astral Sea (my expected preparation time evaporated during a big crunch at work). I'm running Buffy: The Vampire Slayer this upcoming weekend (Slaying Solomon). While that game uses a narrative structure modeled after three-act television dramas, there does seem to be some potential applicability for the countdown clock technique. It would seem obvious to use a countdown clock to represent the transition between acts. But I don't think it's a perfect fit, mostly because hitting act transitions is a bit of an art and not one that is easily modeled by a simple diagram or state machine.
That being said, I think subplots are ripe for modeling using countdown clocks. While a single episode of Slaying Solomon typically has a plot that must conclude by the end of a session, subplots and seasonal arcs can meander a bit a from episode to episode (especially this early in a season).
Anyway, I have some countdown clocks in mind but I may hold off on posting them until after Saturday's session.