Heres my idea: Its a 2 bug combination game.
Bug #1: "Mystery Box" -get a latching box like 3 inch x 3 inch - something small, and place money or trinkets inside it. Then (the box must have a padlock hole) lock it with a padlock, or masterlock type lock. Attach the tag and set loose near your home.
Bug #2: "Key to the Mystery Box" Its the key to the padlock, with its own tag. Set this loose on the other side of the country, while on vacation or something.
On each TB's page, have a description of the mission and a link to the other bug's page. Mission is to look where the other bug is, and move each one toward the other. Eventually, they should meet up somewhere close to each other, where a lucky cacher can grab both, and open the box, getting the reward. Then, have them refill it, and re-release each piece far apart to see them come together again.
You just have to stress not cheating by holding on to one part for a long time, or cutting the lock, etc.
It would be fun to see them getting closer together. Like one piece in San Diego, and the other start in Maine, and end up a year later in Oklahoma City, where someone finally opens the treasure.
Lt.Dan