What is the AirLift system?
God's gift to this world when working on cooling systems
It's a 2 part system that will pull somewhere around a 90% vacuum on a cooling loop depending on your air supply pressure. (Units on the gauge are rated in inHg, with 30 being full vacuum, I'll get around 26-27). From there, you can either seal the system and observe pressure - leak testing. Though of note, because it's under vacuum, it's not perfect. It's possible to get a goofy seal that seals under vacuum but leaks under pressure.
But what it'll also let you do, is fill the system with coolant, using the ΔP to draw in coolant. End result is something that's +/- perfectly bled without turning the engine over.
Depending on the vehicle, it can save quite a lot of time trying to purge air from the system. These rigs aren't too bad, just need to watch air-locking the water pump on fill. But others? Like some specific VWs, fords, or porsche, you can easily be there fussing for 30-45 minutes dealing with 3-4 little bleed screws on the thing and air locks and just being generally lame. Also great for vehicles that use an electric water pump (looking at you BMW) that would normally need a rather $$$$ scanner to run a bleed procedure.
It's generally not a tool you'd need for a home-gamer gig. Cost/reward, and you definitely won't power it with your standard pancake compressor. But boy howdy is it a great one when you start dealing with tricky stuff.