I use the gps on my phone, a Nokia 5800. The maps for China are great, it has the proper gps hardware, unlike the iPhone which uses phone towers for positioning.
It isnt good at storing points that are away from roads though.
When I go to Hong Kong in a few weeks, for yet another visa run, I will buy a dedicated bike mount, instead of keeping it in my pocket, or if it is raining, in my bag.
c