Interesting article about the 747's system for making sure pilots are awake. There's a somewhat similar system on some newer G1000 aircraft (at least the Cirrus), where under certain conditions, if the pilot doesn't respond to inputs, the plane assumes they've lost consciousness due to hypoxia and begins an automatic descent. Cool? Scary? A little of both?
Everyone seems to have a different policy on when to reject a take-off. Some very good instructors will reject for "any abnormality." It's true, better to be on the ground wishing you were in the air than in the air wishing you were on the ground, but consider what abnormalities are worth aborting for. I've never met a piston single that doesn't fly just fine with a window open or a door unlatched. (Except for the Pitts canopy, make sure that thing is on securely!) If you notice at 10 knots your door is open, fine, bring the power to idle and shut the door, if you like. If you're at Palo Alto on our 2,400 foot runway and you notice the door to your SR20 is ajar at 55 knots, for the love of god, complete your normal takeoff, perform a normal landing, then deal with the door. If you're heavily loaded on a hot day, you're probably not going to get stopped in time.
It also doesn't work to have a speed trigger. We're not flying heavy jets with a V1 speed where we continue the takeoff even after an engine failure. If you have an engine fire, abort the takeoff regardless of speed. If the window pops open on your Cessna 172, I would continue the takeoff regardless of speed.