I know I'm raising the dead with this thread but thought I'd mention a very cool safety app from the Ag & Fish Department - GPS Hiker Tracking Service
"It is a free service and all it does is (once activated) automatically sending details of hikersâ€™ locations to the Communications Association of Hong Kong, via mobile or Wi-fi networks. In cases of emergency, family or friends can report a missing hiker to the police and the association will e-mail the location data."
The app also has a lot of country trails on there, so it's worth downloading.
Reading through the previous posts about the GPS vs. map and compass controversy, there is no right answer. A GPS is only good for as long as the batteries last, but you can't use a map in the dark if your torch batteries have died. A compass is only useful if you know how to use one, and how many people know the magnetic variation to allow for in HK? (http://www.scrambling.hk/wiki/MagneticVariation)
I think the answer is to use both, and have a torch with good batteries.