Back in 2008, Liquid Robotics unveiled the Wave Glider, an unmanned maritime vehicle that can travel vast distances across the ocean, collect data, and return for maintenance without ever requiring a ship to leave port.
Yesterday they began the Pacific Crossing (PacX) Challenge Expedition, explained here:
Liquid Robotics launched four Wave Gliders that will attempt to travel the longest distance at sea ever completed by an unmanned marine vehicle. The robots will travel together to Hawaii and then take separate routes across the Pacific, one pair arriving in Japan and the other in Australia. While at sea, the Wave Gliders will be routed across regions never before remotely surveyed and will continuously transmit valuable data on salinity and water temperature, waves, weather, fluorescence, and dissolved oxygen.
The gliders can be tracked in Google Earth by using this KML file or the PacX Gallery page.
You can learn more about this event from the Liquid Robotics PacX page or this post on the Google Lat Long Blog.