Tripwire

A Tripwire is a small, black wire that can be placed with String. Tripwire can output a redstone signal when walked over if configured correctly.

Usage
Tripwire can be activated to output a redstone signal, yet it must be attached to two Tripwire Hooks on each side to output the signal. Tripwire can be connected to other Tripwire for up to 19 blocks. When a Tripwire connection is formed, the Hooks must be placed on both sides of the connection for it to have the ability to be activated. To activate a Tripwire when it is connected, an Entity (only mobs, animals, or players) must walk over it. The redstone signal must connect to the Tripwire Hook to be activated, not the Tripwire itself.

Placing and removing Tripwires
Tripwires are placed with String. The actual Tripwire block can only be obtained through inventory editors or /give. This item can be placed like normal String can be placed. Tripwires connect like Redstone wire, and can connect to Tripwire on all four sides. Tripwire can be placed in the air, by placing it on top of any solid block. Tripwire can also be placed on other Tripwires. When breaking a block below Tripwire, the Tripwire is broken, activating the signal and String is dropped. If Tripwire is placed on Glass or Leaves, it will not connect to Tripwire Hooks or Tripwire placed on any block that is not Glass or Leaves. Yet, when a the Leaves or Glass is broken, the Tripwire is not dropped nor activated (the Tripwire remains in the air). This the same for when one is broken that has another Tripwire placed on top. Tripwire has the same function when in the air as if it was on the ground. When breaking Tripwire itself, it activates any Tripwire or Tripwire Hooks that it was connected to. To disarm Tripwire without activating the signal, you must break the block with Shears. This will remove the block and drop String, yet will not activate the signal. Tripwire has the hitbox of a Slab when it is not connected to Tripwire Hooks. When it is connected, the hitbox is the same as Redstone wire.

History
Tripwire was first revealed on Dinnerbone's Twitter. Dinnerbone released a video showing him experimenting with Tripwire before it's release. The video is below.

Tripwire was released in Snapshot 12w22a.