Silly APRS idea

This came up on freenode #hamradio channel: little floating APRS buoys set afloat in the ocean, with a GPS receiver and a digipeater.  You'd have to program them to alter their operation based on where they are, because APRS frequencies vary around the globe, and in some places operations might not even be permissable.  Getting a few operating in the North Pacific Gyre could provide interesting scientific data to boot, especially for those people tracking flotsam patterns in the Pacific.

No idea what it would cost to build a APRS buoy, and certainly nothing I'm planning on doing any time soon, but could be interesting.