Deadman Switch For Website

I hate to sound morbid, so think of this as possibly a "sitting in a hospital bed, too sick to modify website" switch as well.  If, for any reason, I was too sick or dead to get on the web and modify the ScopeRoller website to indicate that I could not fill orders, I would like for the site to stop accepting orders.  At the same time, I don't want to make the cutoff on the PayPal side of things, because contributions drip in occasionally that way.

Ideally, I would upload a replacement for the part of the ScopeRoller website where the user clicks buttons that place orders so that the buttons were either disabled, or put up a message that said, "Due to illness, this website is not currently accepting orders."  I suppose that I could set up an FTP script to upload a modification to the code shared across all the different pages to do that, and set it up to run every week, but I really only want that to run if I haven't explicitly told my PC, "Hey, I'm still here."  Or should I just leave an FTP script to do this that is simple enough to leave to next of kin to run?

Any suggestions?