> - We're using a vibe coded app on an iPhone that does terrain matching and target finding.

And that part seems entirely reasonable. It looks like the Tomahawk cruise missile did it with an 84 lb package with a 16-bit computer with 64K of memory [1] [2] and sensors. That's similar computing performance to an original IBM PC, which weighed 30 lb. The only bit of hardware an iPhone doesn't seem to have for TERCOM is a radar altimeter, but it looks like those are available for civil aviation.

[1] https://www.forecastinternational.com/archive/disp_pdf.cfm?D... ("AGM-109/BGM-109 Tomahawk ... Litton 4516-C digital computer with 64K memory")

[2] https://www.forecastinternational.com/archive/disp_old_pdf.c... ("16-bit LC-4516C digital computer")

Or something newer, like this one: https://www.garmin.com/en-US/p/166298/#specs