Good tip! That's a new one, I'll try it. Sounds very good, and I've already got the extract on hand.
I'm a real green tea enthusiast, so I'm really appreciating your interest. We also have a whole thread dedicated to specifically green tea, if you haven's seen it yet:
Anybody drinking green tea for weight loss?
There's some other tips in that thread as well. But your vanilla extract idea sounds like a definite winner!