From what I have read data speeds are slow (2.4Kbps). which is slightly better than dialup. I would not expect a fluid response with bandwidth thirsty apps like netflix, youtube, facebook, etc.... (I wouldn't expect such apps to be usable on such a slow connection)
Although data speeds are reportedly to increase (1.5Mbps) when Iridium "Next" rolls out in 2015 (according to Iridium). 1.5Mbps is still significantly slower than broadband connections of ten years ago but could pass as acceptable in a wilderness setting.
Thanks for the info on data speed! Where did you find that information? I looked but was unable to find anything about speeds.
..... How much energy to bring along (extra batteries) and can any energy be transferred in the field? (More batteries and adapter cables to bring along)
In the moment of need I prefer to turn my handset on and make a call. A connection between GO and the smartphone is required and fumbling around with a smartphone menu and wifi connections is not something that will decrease the time of initial communications. That could be a problem if you are depending on a non-techie person in your group to get the devices to "talk" to each other (and you are the one in need of help).
Depending on one device working rather than two seems to me a better bet. I see this device and others like it terrific for casual communications.
I don't see this as a replacement for PLB, SPOT, Sat Phone, etc. However it could be useful for more than just "casual communications". My interest if rather for quickly setting up an Incident Command Post at a remote trailhead, for SAR operations.
The initial response for a typical SAR search mission might involve an Incident Commander sitting in a pick up at a trailhead, and perhaps 3-5 Strike Teams out in the field. The IC will be talking to the STs via hand held VHF radios. While the STs are deploying, back in town others are gathering more information about the subject. A persistent problem in these kinds of missions is the lack of cell coverage at the trailhead. The IC needs to be able to communicate with the folks in town.
Having even a relatively modest speed data connection would be extremely valuable. The in-town folks can transmit more info on the subject as it becomes available (a recent photo of the subject, or the latest weather forcasts for example). The IC at the trailhead can send back photos of clues discovered (for example "...This is a photo of a jacket we found on the trail, ask the subjects wife is this is his?...") The IC can also be checking the availability of more resources, etc.
If the mission grows in size and complexity, the IC will get additional help (perhaps an Ops Section Chief, a Planning Section Chief, and a Staging Area Manager) so the ability to link several smart phones or tablets would be extremely useful. Even 2.4Kbps would be useful, and 1.5Mbps would very helpful.