Sony have unveiled the LocationPorter RVT-SD100, a "realtime video transporter" intended to stream footage from a connected camcorder or camera across whatever connection is available, to a second remote LocationPorter device. Although you can hook the LocationPorter up to a wired LAN connection, it really comes into its own with a 3G data card or two: the streamer is able to combine both connections to support up to a 352 x 240 64fps video at 320kbps.
Video demo of the Sony LocationPorter in action after the cut
A single 3G card can manage a video of the same resolution, at between 5 and 15fps with bitrates from 64 to 160kbps. Meanwhile find yourself a nice sturdy LAN hookup and you can scale that up to 30fps at 1024kbps max. The RVT-SD100 uses the H.264/MPEG-4 AVC codec.
No word on pricing or availability, and this does seem like a product intended for mobile pros such as reporters and deep-pocketed bloggers: especially as you need two LocationPorters for it to work. For everyone else, one of the numerous mobile streaming clients for cellphones - such as kyte.tv or Qik.com - would be an easier way to share impromptu footage.