I've done quite a bit of research on this in the last half year. I initially found some very expensive pro broadcast solutions in the +$10k range. After that I came across some simple hardware devices, sub $500 that could be daisy chained to add even more connections. And then of course there was software solutions, which is the cheapest or could even be free.
But what it all came down to is that none of the solutions, aside from perhaps the pro broadcast one, will actually combine bandwidth for a single session on the same machine. So … if you wanted to upload to two different sites faster than a single connection would allow, this could be possible, but to use multiple connections to upload to a single site (in the same session) wouldn't be possible, because you would be using multiple ip's, and the receiving site would likely terminate both sessions. SO you would have to somehow combine the two connections, and then pipe this to a router that would act as the single ip to speak with the internet. This is a headache, and any hardware that could do it is not of the mobile variety. But it is possible.
With this you could combine multiple carriers such as Verizon and Sprint, or you could even use different bands within the same service, such as combing both the 3G and 1X bands. This will not only increase the total bit rate you can get away with while streaming over mobile connections, but also increase reliability during times when the radio towers are being flooded.
I plan on continuing my research into this, and will share any progress I make toward a mobile solution.