Good points, reefduffer.
Are you only using this in US waters? Do you (or would you) set up a separate MMSI for use in other countries? Or do you just use the same Boatus.com MMSI?
My next trip is Key Largo, so I haven't had to think about that immediately. I definitely want it there, and I think I'm good to go.
Next is Bonaire later this fall, and I haven't decided whether to take it, and hadn't considered another MMSI. The thread
http://www.scubaboard.com/forums/abc-islands/410653-nautilus-lifeline-bonaire.html is interesting reading. Bonaire diving is less likely to cause a "left behind" situation, and there's the weight restrictions, theft risk, etc. to consider. But once I've got it, it's tempting to take it for chat functionality (my wife has one also), and "just in case". Assuming anyone in Bonaire might notice a DSC call. In that thread, some experienced Bonaire hands said they'd rather carry a cell phone.
Mike Lever said in that thread that Bonaire authorities have approved the LL and it's being sold there.
My understanding is that assuming you have an MMSI entered, so the LL will send a red button DSC distress call, having a regionally correct one won't impact anyone hearing the call, understanding it's a distress call, and getting your GPS coordinates. It might impact quick ID of who you are, but that's not that important to me. And if I really do press the red button and later get fined for a foreign MMSI, so be it. It's still unique, identified as from USA, so it's not like I'm being clandestine about who I am. And I'm not really sure it's even wrong to use my "Home Port" MMSI, I think that's what I'm supposed to do.
I admit my incomplete knowledge there, and would welcome informed correction.
Would there be anything that would prevent you from, say, reconfiguring the MMSI with just your Mac for a dive trip?
I just started the app on my Mac and connected my LL. I'm given a menu in "General configuration" to change the region. Choices are limited: Bahrain, Canada, Egypt, International, Maldives, Saudi Arabia, UK/Europe. The manual says to set it to where I'm diving, but I don't know why "International" would add value over USA for Bonaire diving.
But the menu seems live, I expect it works. I don't feel inclined to test it, though. Keys trip coming up too soon to mess around.
As for MMSI, it looks like it requires Nautilus customer service (remotely, I think) to reset it so you can enter another one (for Windows users too). From page 7 of the manual:
"...You can only enter your MMSI number once, and you can only enter one MMSI number. If you need to change it or add a new MMSI number, contact Nautilus Lifeline in order to reset your MMSI number to the default 000000000. See Customer Support on page 22. ..."
There's a PITA, and an added disincentive to changing it for travel, and a reinforcement that maybe you're not expected to. I have no idea if this requires a Windows PC like the original registration, I guess that's at least plausible. You'd have to ask Nautilus.