Kona Brewing (perhaps, not surprisingly) makes a passion fruit wheat beer. The name starts with an A and is very Hawaiian sounding but I can't recall it offhand. It's too sweet for my liking but the passion fruit is really present, maybe too present. The idea seems sound, though. I scraped the seeds and insides of some way ripe passion fruit and stuck it in the freezer with the same idea in mind...although mine might go into EdWort's Apfelwein recipe instead. Keep us posted!