set theList to every paragraph of (do shell script "sudo softwareupdate -l")
set updates to ""
repeat with anItem in theList
    if anItem starts with "   * " then
        if updates is not "" then
            set updates to updates & return
        end if
        set updates to updates & (characters 6 thru -1 of anItem)
    end if
end repeat
if updates is not "" then
    tell application "Finder"
        ignoring application responses
            display dialog "Software Update available:" & return & updates with title "Software Update available" buttons "OK" default button 1 with icon file ":System:Library:CoreServices:Software Update.app:Contents:Resources:Software Update.icns"
        end ignoring
    end tell
end if