Thom,
Li Hing Mui, or Li Hing Powder is a red powder made from the extract of plums. It's salty, sweet, and quite sour all at the same time. It's hard to describe, but you can do anything with it. Bake, make drinks, anything. It's a great powder to coat things with such as dried fruit or in Pablo's case, Gummy Bears. Pablo bombed me recently with sour patch kids dipped in this mystery powder. He's most likely the expert in this stuff, I'm pretty new to it. Just a few years under my belt.
In Hawaii, you can find it everywhere (well, at least where the locals are), and here in Asia, particularily around the Chinese, you will find in everywhere as well.
If you like sweet/sour you will love it.