This New Zealand hiker found a man lying in a stream in the woods with a head injury.
The hiker used his PLB to summon help (no cell coverage), but the helicopter had trouble locating them due to the tree canopy, and (judging by the photo - see linked article below) there was no place to land nearby.
The hiker found a spot of sunlight and used his signal mirror through a gap in the canopy to signal the helicopter. ( Since he's in a Commonwealth country, he refers to it as a "heliograph mirror").
A paramedic was winched down, and the victim winched out.
NZ Herald - Inventive tramper saves hurt man's life (This earlier NZ Herald report gives the paramedics name and the date (March 31st), but doesn't mention the mirror.)
http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=11230314