Wii Transfer provides basic AppleScript support for converting movies for viewing in the Wii's Picture Channel. You must specify both the source movie file and destination location in your script.
Below is an example AppleScript.
tell application "Wii Transfer"
convert movie "/Users/your-user/test-source.mov" to "/Users/your-user/test-for-wii.mov"
end tell
Wii Transfer looks at the file extension for the destination movie to determine how to convert it. To convert a movie to Motion JPEG for storing on an SD card, use the .mov file extension. To convert a movie to Flash Video for streaming using the Internet Channel, use the .flv file extension. Note that for Flash Video, the files must be placed inside Wii Transfer's movies cache folder to be available on the Movies screen from your Wii.
For more information about AppleScript or using Script Editor, please consult your Mac Help.