Hitch hiker
From GeoWiki
Hitch Hikers are items in Geocaches which are tracked over time. The first Hitch Hikers were objects with a logbook attached to them. Cachers would write their name in the logbook and put the item in another cache.
Geocaching.com then introduced Travel Bugs which were a coded dog-tag which could be attached to items. These cost about A$8 per bug.
Geocaching Australia has released free Hitch Hikers called Swaggies.