this is the best I can come up with, but I'm no expert. Can't guarantee it will work as I don't have/can't get vlc on my phone but it does try and open the file once the download has started.
Basically you need to find the package and activity name of the application that you want to start (have a look here or google it
http://simrandev.com/coding/launch-a...-adbterminal/). I just fired up adb logcat and started a video to find the activity.
The -d parameter is the location of your rtmpdump output file.
rtmpdump -r -W etc -o /sdcard/test.flv | am start -n com.cooliris.media/.MovieView -d /sdcard/test.flv
The standard android movie player doesn't handle flv so I just got an error saying the file couldn't be played.