As mentioned in the Satellite phone thread there are a number of satellite enabled gps locators available on the market as alternatives the SPOT and Delorme/SPOT units.  As an avid fisherman and member of a group that enjoys time in the salt aboard what is pretty much a piece of Tupperware, these tools get discussed quite bit amongst that circle.  These tools aren't just in use by fishermen and boaters though, pilots, hikers, SAR teams, and our servicemen all use these as well for good reason.  I've personally been saving up for one in lieu of picking up a SPOT since I refuse to pay $100/yr. for their service.

Here is ACR's comparison of their systems to the SPOT: http://www.acrelectronics.com/faqs/spotvs.aspx#Q1

Personal Locator Beacons (PLB's) are much smaller than their full fledged counterparts, Emergency Position Indicating Radio Beacons (EPIRB's).  ACR has been in the game for much longer than SPOT and makes some very tough PLB's that capable of sending limited messages of "I'm safe", "I'm Here" w/ location, and their original function of a distress call.  The two service levels are about half the annual price of the spot messenger service ($40 basic, $50 "plus").  This particular service currently has a limited service area, but the gps-enabled distress beacon function works anywhere on the planet.

The EPIRB's are primarily used on marine vessels due to their power and functionality.  For some of our more worldly overlanders I think there could be some benefit for going for one of these "whole enchilada's."  Some of these are even capable of integrating with your other electronics [possibly APRS?] you may have onboard.  These units are also capable of the same messenging service.

Here is the link to ACR's homepage: http://www.acrelectronics.com/default.aspx

Reading ACR's comparison of their products versus the SPOT leads me to believe that you could argue the two products in much the same way as the CB vs HAM debate.  Our densely forested terrain here in Western Washington and Orgeon strains satellite based coms.  If my life were in the balance I would want to make darn sure that my beacon would be heard/found.  I think this highlights one of the key differences between the SPOT and PLB.  The PLB is primarily for safety and rescue whereas the SPOT has a more recreational focus.  If you are in dense forest you may inadvertantly freak out your significant other when SPOT doesn't send out a breadcrumb or two due to poor reception.  I think it creates an artificial dependency.  There is a third PLB (McMurdo Fast Find, $300) out there on the market, but it is strictly a rescue beacon without messaging capability.

Here's the cost comparison:

	Unit	Year 1		Year 2		Year 3		Year 4		Year 5		Year 6		Year 7		Year 8
SPOT w/service	$120	$100	$220	$100	$320	$100	$420	$100	$520	$100	$620	$100	$720	$100	$820	$100	$920
ACR PLB-350C w/ basic service	$430	$40	$470	$40	$510	$40	$550	$40	$590	$40	$630	$40	$670	$40	$710	$40	$750
ACR PLB-350C w/ plus service	$430	$60	$490	$60	$550	$60	$610	$60	$670	$60	$730	$60	$790	$60	$850	$60	$910

Here's some info on useful life:

- ACR PLB 11yr useful life, 5yr warranty beforeservice required. http://www.acrelectronics.com/support/useful.htm

- No data available from SPOT other than $30/yr replacement plan. 1 yr warranty.

Here's some more interesting info on the net about SPOT and other PLB's:

http://14erskiers.com/franksblog/2010/06/spot-gps-messengers-worth-it-or-worthless/

http://www.equipped.com/

http://gpstracklog.com/2010/02/spot-gets-some-competition.html

Craig- I probably should added the caveat that the real value of that post was contained within the comments.  A representative from SPOT actually responded to the post and addressed some of the questions.  The second and third links may actually be worth a read if you're considering laying your hard earned dollar down for any of these devices.

At the moment I own neither of these devices because I'm having a hard time deciding what I'm really wanting out of the device beyond the obvious.  If it isn't readily apparent I am leaning more towards an ACR PLB.  The fact that the device performs its fundamental function independant of subscription-based services is a huge bonus for me and ensures that I'll keep it around JIC.  The messaging function is just a bonus or luxury in my opinion and I'd like to know I didn't waste $200 for a service I don't really need, in which case it breaks even after just over 3 years without the additional service on the PLB.  If I want to leave breadcrumbs for one or two trips a year $40-60 is easier to swallow.

Cell phone is not a competitor to sat phones per say, they both serve two different applications in my mind.  The issue is the small amount of sat users (somewhere in the 225k range) do not generate enough revenue to launch and maintain an array of satellites. 

The only reason GPS is still around and so prolific is our tax payer dollars built the satellite network for the government and they are nice enough to let civilians use it for free.  If the GPS products had to pay for the network itself I bet they would find the same peril as sat phones.