The daylight sensor was released with the 1.5 update. This can serve as very useful on nonpvp survival. What the sensor does it what it says. It senses daylight and sends the signal to redstone. When its brighter out the signals stronger and when its darker the signal decreases until it ceases. It can recieve light through blocks (I'm not sure how many) and torches or other lighting methods won't set it off, only daylight.

What you can use this for is to create an autolocking system on your house. While you're away from your house at night you can imagine whats happening to it, lots of creepers and other hostile mobs getting in because you left the door open. If you utilize this item than that is no longer a worry.

What you can do with this is set it adjacent to the blocks next to your door, or set up a redstone wire. When its day your door is going to be wide open. Hopefully no mobs are going to get in because hopefully your house is in an opening and they'll burn up trying to get there.. During the night when they want to mess with you they can't get in as the door is shut because its not recieving the signal anymore.

You may say hey, they'll still try and break the door down. That's true, but this doesn't make your house unbreakable, it just makes it more secure by shutting the door if you forget to. Even so, as long as you or nothing the hostiles want is in your house then they won't break your door down.

The most probable use for this would be this auto locking system although there is another probable use that may be even more adventuresome in my next post.

the photo shows you both sides of the spectrum and shows you that torches have no affect.