The good folks at Shandy's Place sent me the link to this article
http://online.wsj.com/wsjgate?subURI...DYzNTA1Wj.html
The SPOT device sounds very intetesting. Not exactly a PLB, and it sounds like it is a subscription service ($), but in addition to an emergency "Help!" message, it can send limited "I'm OK" messages whenever you want.
If you Google "globalstar spot emergency" (without the quotes), there are a ton of references.
Bill