I have been doing some tests with a Teradek Vidiu, it takes a HDMI in and can stream live directly to youtube (among others). Seems to work good so far. I have been using it with a GH4, and it can be battery powered with an adapter. It does support 3G usb modems but I don't think the bandwidth will be enough to be useful, especially not during live events with lots of other people using the 3G network.