Beacon Cache
From GeoWiki
A Beacon Geocache is a Multi-cache that uses technological means to fine one or many subsequent waypoints; May require specialised hardware and/or software to complete.
Examples of technology that could be used include:
SPOT active GPS trackers. GCA has done some testing on these andcan facilitate auto-updating of your cache should you decide to use one of these devices. Contact the admins for more information.
Garmin Chirp Beacons: (see [1]) : These devices allow you to act as a stage in a multi-cache and send the next co-ords to the finders GPS Unit. NOTE: These currently only work with a subset of Garmin Devices with specific hardware and firmware configurations, thus potentially limiting the potential finders.