I work for Transitions Optical. Original Transitions lenses are activated only by UV light, not visible light or light emitted from a GPS unit and, as somebody else had mentioned the change is gradual, not instant. In my own personal experience, I know my glasses need a good cleaning from the salt spray every time I come off the water. Perhaps it was that, or just could’ve been a coincidence.
Maybe we should get a techno-geek on this, but I am under the impression that LCDs and certainly CRTs (old style computer monitors) DO emit some UV light. Although the amount LCDs emits is less than CRTs. The UV in LCDs come from the flourescent lamps in them. The new LED LCDs don't have these flourescent lamps and apparently emit 0 UV.
However, I am not disputing the cause was other than this, I was just trying to get others experiences and thoughts. Answer me this Batman, staring at a GPS screen in the dark of night for extended periods of time, or staring at it to get a reading for say, 10-20 secs. Perhaps that is enough time to turn out the lights so to speak?