We purchased two Inmarsat IsatPhone 2 satellite phones (along with a basic monthly subscription plan through BlueCosmo) so that I will be able to make contact with my family in case of emergency while traveling (which I do frequently for work). During emergencies cellular networks might go down due to power outages or damage to the physical infrastructure of the network, or be saturated by callers using the network to contact their loved ones.
Not all plan details etc. are super-evident when researching satphones, so I will provide some additional information based on my experience so far.
1) I learned that though only a very small number of satellite phone networks exist (with coverage in the Americas - only 3: Inmarsat, Iridium, and Globalstar), all calling plans are sold through a secondary vendor (in our case, BlueCosmo).
2) We chose Inmarsat for a combination of reasons. Price was one factor (the phones & minimum monthly calling plans are cheaper than Iridium), plus near global coverage (Globalstar only provides coverage in the Americas). Apparently, service is absent at the poles - but I don't have any antarctic travel expeditions planned (yet).
3) The biggest difference between Inmarsat & Iridium is that Inmarsat uses a small number of very high geostationary satellites. This means that you need to have 'line of sight' towards the equator to use your phone. I wondered if this would mean that at high latitudes we would need to be in a large open area to call, but in the northeast U.S. (at least) this was not the case. I was able to call easily from within a tree-enclosed driveway, This must mean the satellites are very high, and that the LOS required is thus at a fairly steep angle!
4) After purchasing the handset (which is pre-packaged with a sim card), you need to select a pre-paid minutes or a monthly post-paid calling plan. We chose the latter - but the most basic plan, which is about $35/month. We decided on a monthly calling plan because we purchased the phones for emergency use and we do not know when emergency will strike. All pre-paid plans expire, and the costs are comparable. (For instance, the cost for a 6 month pre-paid calling plan with the minimum number of minutes is not too different from 6 x $35.)
5) The phone itself is kind of fun to use. For those accustomed to the latest smartphone (but older than the age of 35) it may inspire nostalgia because of its physical similarity to a cell phone from the 1990s! Entering contacts, etc., is an adventure.
5) What can I say - the phones work great. Call clarity is similar to a cell phone, and the phones can send & receive SMS and short (max 160 character) emails. I have used the phone to call land lines, U.S. cell numbers, and other Inmarsat phones.
So far, they are serving their purpose. I feel more comfortable traveling know that I will always be able to reach my family in case of emergency & vice versa.

Saved my life when stranded in the Moremi game reserve.

Terrible !!
using it close to my home, in the city, everywhere and I was not able to make a hope call.
today, sept 27 the work hard fo fix the problem, now the phone is working perfect, thanks!!!

Fantastic Sat Phone. I use my for offshore fishing to stay in touch with home. The product is easy to use and setup. For the price, it was well worth it. BlueCosmo service was great as well.

Nice to deal with quick to send. Very nice Item. I recommend