While tee shirt flyers sounds like a cool, novel idea...it just wouldn't get enough exposure. A single person (or a few people) walking around in a tee shirt can only go so far. Only a limited number of people would see, much less actually READ and remember, the advertising. Unless the person wearing the tee shirt is also passing out flyers or other give aways, the "customer" viewing the tee shirt would have nothing to take away. They need to be able to see it again and again for it to "stick".

Keep brainstorming though. You may hit on something else that is more doable.