gravity victim, many commercial airliners have peep-holes in the cockpit door. I think you may be on to something with cabin surveillance. What do other pilots think of being able to monitor the cabin with monitors in the flight deck. It may provide valuble seconds...
As for arming pilots, I'm a little weary about having anything that can be turned against the flight crew, guns, tazers, etc. Personally I'd like to armed, but once the hijackers know that all pilots carry weapons I think that ultimately flight crews would be in greater danger should the unthinkable occur.
Hijackers wouldn't have to smuggle guns through airport security, they'd already be on the aircraft.