Love to hear ideas on what you'd wire this up to - eg. What kind of device or process do you want to trigger once lightning is detected?

A camera! The 2.5mm TRS remote trigger jack just needs one of the pins connected to the sleeve to trigger the camera, very easy to do with an optocoupler or even relay.

Usually, lightning detection is necessary for regulatory compliance. Facilities with pools need to remove patrons to prevent risk of electrocution, summer camps need to move people to enclosed shelters, as with golf courses, construction sites, beaches/waterfronts, etc.