Grounding all 737 8's and 9 series now prevents another....for awhile. I've been thinking on this...and IIRC, there was a great deal of fanfare demands for remote control capabilities for aircraft even before 9/11 to prevent hijackers from gaining control of the plane.  A system then was described as being one which could NOT be overridden by anyone onboard.  I think that's the system we now have, by design. (Though, I have heard a Boeing rep state that the pilot could have disabled it).  A software app like that could easily be used to remotely fly a plane into the ground.  No one counted on that intent (a little hard to believe). But, seems software modifications could change things in short order.