I realize I'm a little late on the trend with this one, but I recently discovered these lip tattoos, and I really like them. Basically, they work in the same way as a temporary tattoo; place them, wet the backing paper, let them dry.
Then all you have to do is apply a little bit of lip balm over the top to stop them from drying out and you're all set!
I got mine from eBay for a little more than a dollar each!
You can find the ebay seller I bought mine from RIGHT HERE!