Icky semi-pseudo-code for the pi thing

gistfile1.py

url = "http://whatever.com/"
reference_page = ""
current_page = ""
wait_time = 5 * 60 #seconds

setup( )

while True:
    download_page( )
    if not same_as_reference( ):
        if page_shows_warning( ):
            flash_and_stuff( )
        save_as_reference( )
    wait_a_bit( )

def setup( ):
    # set up pins, mixer, whatevs.

def download_page:
    current_page = stuff

def same_as_reference:
    return current_page == reference_page

def page_shows_warning:
    # XML parse some shit
    return True

def flash_and_stuff:
    # play sound
    # flash lights

def save_as_reference:
    reference_page = current_page

def wait_a_bit:
    time.sleep(wait_time)