I think I like the idea of a trackable spirit best. That way more people get to see it. But there's no telling what kind of containers it might get stuck into while it travels. Would it be possible to weather proof it a bit? Make it out of a different material or something?

It's probably possible. Could laminate the card, too.

Love the geocaching idea, further tying the game to the real world. Also, +10 for the QR code idea. It's a great way to convert peeps who discover the cache by accident too.

Bad idea only cause spoofers would take the fun from it

Er... forgive me, but how would they manage that?

Headcount... how many geocachers do we have here?

never heard of geocaching.. but read into it a bit.. and by the looks of it theres tons of cached around me and special geocaching meetings in my city too