There are 50 Health Shrines scattered throughout Sleeping Dogs' Hong Kong, and for every five you find Wei gains 10% health, eventually doubling his life total. They're scattered all over the place, and the easiest way to find (and track) them is to complete one simple mission that will instantly show you where every single one is.
Early in the game you'll meet a blonde American tourist named Amanda (voiced by Emma Stone). After a few missions showing her around Hong Kong you'll be offered a mission called Photographing Amanda. It's a simple, combat-less mission, requiring you to follow Amanda around taking pictures. Once it's completed, every health shrine will show up on your map, making it easy to travel around, increasing Wei's health total.
But if you don't feel like doing that, and just want to know where they all are, we have that for you, too...