Does flash provide an api to deal with remote stream like IP camera does?
Axis has a number of IP cameras that directly support RTMP:
Wowza can re-transmit an RTSP stream as RTMP. It's not necessary to actually transcode to do this. The same video can be transmitted as either RTSP or RTMP and it's just a matter of different transmission protocols. Software can capture one and retransmit the other without actually transcoding the video.
http://www.wowzamedia.com/forums/showthread.php?t=6470
I was sure FMS supported this too, but I couldn't find any definitive references.
Here's an example where someone connects to an Axis IP camera and rebroadcasts the image to FMS for streaming to Flash (which involves fully decoding and re-encoding):
http://www.geekorgy.com/index.php/2010/06/ip-camera-to-fms-flash-video-howto-osx/
Here's an announcement that the first IP camera with built-in RTMP support exists, although either I'm blind or it fails to mention which camera it's referring to (or perhaps it's just an early beta and thus not mentioned):
http://groups.google.com/group/c-rtmp-server/browse_thread/thread/f5de18f4e8b5ea5f