SVC, or Scalable Video Codec, can dynamically change the resolution and bit-rate of video streams. This is extremely important for security applications as so many viewers are in remote locations. It's is especially relevant to megapixel cameras that stream at very high bit rates (relative to WAN bandwidth) and can easily cause problems for remote viewing. For more information on SVC, see an overview on SVC posted on the site last year. It's going to take some time for SVC to go mainstream (as it requires more processing power but it will address the increasing pain as megapixel camera use expands).
In the meantime, there are a number of techniques video surveillance vendors are providing. One popular technique is for the NVR/VMS system to transcode video before it streams it to clients, enabling the bit rate to be dynamically adjusted for remote viewers (see 3xLogic's Aztec CODEC and Salient's Dynamic Resolution Scaling). Another alternative is Avigilon's use of JPEG2000 which provides scalable video but lacks the bandwidth efficiency gains of H.264.