BTW some info on SPOT vs ELT/PLB is well discussed by Doug Ritter of
Equipped to Survive

see

http://www.equipped.org/blog/?p=82
and
http://www.equipped.org/blog/?p=83

Doug Ritter did some great work previously with problems with PLBs,
design issues and holes in the standards, you can fish around his blog
and find out more about that.

Darryl