If you place an TNT and on the world while this Behavior Pack (Instant TNT) is loaded, the TNT will automaticly ignited and after four seconds it will explode. And the best is: IT HAS A TIMER ABOVE IT!!

A Video about this Addon (note that the video is old):

Note:

• It only works if the player has the tag "instantTNT" (/tag player add instantTNT)