Given enough evolution of the technology, the stream of new Bitcoin transactions and blocks could easily be fed in through a satellite downlink - the same way XM Radio, DirecTV are downlinked.
This is no joke. Satellite downlink is a simple one-way stream of huge amounts of data, and those streams can and do contain all kinds of things you would never expect. If you've ever noticed "XM Traffic" on a car's nav system, you've seen one basic example. If you've ever seen your satellite TV receiver update its own firmware over the air, you've seen another. Same yet again if you order a pay-per-view movie and your receiver suddenly knows you paid for it the minute you do so, even though the receiver unit itself may not be connected to the internet.
If you've ever been the pilot of an airplane that supports XM's aviation downlink product, there's gobs of other information being downlinked through the very same satellite signal feeding tunes to your car on the highway - such as locations where lightning has struck recently, text-based weather/visibility condition reports at airports ("TAF's"), all of the doppler radar across the continent, and much more specific to the aviation industry. All of this occupies a tiny slice of the total available bandwidth available in that satellite signal, and it's very profitable for the satellite companies to offer it, in terms of what they can charge for that feed.
http://www.xmwxweather.com/ground/data-service-pricing.phpThe Bitcoin block chain is no different. With nothing more than a satellite feed, in theory you'd have everything you need to be a Bitcoin node, without the ability to send transactions.
Where there is a worldwide demand for a data stream, especially a relatively small data stream whose cost to acquire is nearly zero, the business case for a satellite feed is easy to make. Bitcoin bandwidth requirements will grow over time of course, but just look at how many channels you can get over DirecTV today - easily into the gigabytes per second - Bitcoin transaction volume has a lot of catching up to do to fill it. Meanwhile, you'll have demand for multiple providers of this feed, as people will cry "centralization" and worry about economic crippling if there's just one. (similar to GPS vs GLONASS etc). So we could easily see "datacasts" of block chain data being packed into unused bandwidth of TV signals etc. and multiple independent ways to get block chain data off the air.
http://en.wikipedia.org/wiki/DatacastingOn the other side, sending individual outgoing transactions could be accomplished over regular radio waves, being short blasts of information that travel one-way on a best-effort basis no differently than a distress beacon. Imagine you're a hut selling bananas in Africa and use solar to power your gear. Doing a transaction might consist of nothing more than blasting it out on the open airwaves and then looking to see it relayed from the satellite signal within the next few minutes, trying again if not seen. All of this on battery or solar or electromechanical power, no less.
I don't necessarily mean blasting the transaction back to the satellite (though it's certainly one of the good possibilities), but I am thinking more that you could blast a transaction using a low-cost transmitter with a range of a few kilometers, and expecting that somebody on the ground in range of your signal will either have internet access or the ability to forward the transaction somewhere else that does. This would make the equipment needed to send new transactions simple and affordable, not to mention keeping it anonymous and open to anyone without needing a costly satellite "outbound data" plan.
In areas with sparse infrastructure (like Africa), highly directional antennas and installing them pointed at known receivers would easily extend that range into the tens of kilometers. Better yet would be the definition of a "bitcoin radio protocol" that allowed a bitcoin relay network to form based on loose peer-to-multipeer radio broadcasting rather than an IP network, where transactions would hop over radio waves from node to node until reaching the internet at large. This would be for propagating transactions produced locally and getting them on the wire, not so much for propagating the block chain.
While none of this is achievable for Bitcoin in 2012, if Bitcoin is going to take the world by storm, then being able to transact in this way eventually can be pretty much considered a given. Hello Africa.