I just noticed this excellent review from March 2013 at OutdoorGearLab.com:

The Best Personal Locator Beacon and Satellite Messenger Review

They compare and contrast these Personal Locator Beacons (PLB)s, Satellite Emergency Notification Devices ( SEND)s, and an iPhone app (while emphasizing the extreme coverage limitations of the app). In the bulleted list below, I've hyperlinked Doug Ritter's articles where available.

• ACR ResQlink 406 Personal Locator Beacon (PLB)
• DeLorme InReach Satellite Messenger
• Spot 2 Satellite Messenger
• Spot Connect
• Apple iPhone Find My Friends

At the time of the review, their "Editor's Choice" for a SEND was the DeLorme InReach Satellite Messenger, and for a PLB, the ACR ResQlink 406 Personal Locator Beacon, but of course your priorities may vary, and the market continues to evolve - the new Ocean Signal RescueMe PLB, which was unavailable at the time of their review, seems to competetive with the ResQlink.

I would love to see a thorough review of the Ocen Signal unit. I am always attracted to the lightest gadget that will do the job...

Very handy info, thank you.

Blake

www.outdoorquest.blogspot.com

Mario Vittone posted some comments on his blog about whether the Ocean Signal unit might be actually be too small. Note that he is refering specifically to use in a marine environment, like in a lifejacket pocket. His concerns might not be as significant for use when climbing or backpacking. He has obtained one to test and has promised a follow up evaluation, but so far I haven't see it.

Vittone is a former USCG Rescue Swimmer, now retired. He was one of the volunteers in the Cold Water Boot Camp videos.