Re: Sat Phone?
For true worldwide coverage, there is only one name: Iridium. They work absolutely anywhere in the world you have a clear view of the sky, including the poles and oceans. BUT.... you will pay for it as they are also the most expensive service out there. I used a 9505 for quite a while and it worked in some pretty harsh conditions. The 9555 is supposed to be even better, but I haven't had my hands on one yet.
I've never run on them, but those that use Inmarsat BGAN network have very good coverage and are the biggest competitor to Iridium.
There are other carriers that are more regional such as Thuraya that covers Europe and the Middle East/South Asia pretty well and are a lot cheaper, but you lose coverage in North America. Most Americans that run Thuraya lease the phones for the duration of the travel. I used one for a while and the call clarity and signal strength seemed better than the Iridium for Afgh., but it would also fade out faster with poor weather.
Here's a good set of links showing coverage of the different providers:
http://www.globalcomsatphone.com/support2.html
Unless you plan on using it for data a basic satphone should suffice, and a lot of dealers sell used models that are in pretty decent condition. They can get pretty expensive when they try to turn them into smartphones, and really it isn't necessary most of the time.
Bottom line is satellite phones are useful when there is absolutely no other alternative, but across the board the clarity sucks, the delay is horrible, and the cost is through the roof. I would have never used one at all if it wasn't provided by my employer and a requirement of my job. I don't like them for actual communications that aren't necessary.
For overseas travel a basic GSM phone with either a roaming sim card or one for that specific area work pretty well and are CHEAP.
For your stated purposes (emergencies), I would actually look at one of the satellite emergency devices such as a SPOT. The cost would be a lot less, durability a lot more, and are also capable of linking up with Delorme GPS units. I personally haven't used one of these yet, but it is on my list of future purchases.
http://shop.delorme.com/OA_HTML/DELibeCCtdItemDetail.jsp?item=30786§ion=10741