Is there a block or duct type that will signal when an item passes through it? Redpower had the item detector, and I think there was a pipe type in buildcraft, but there doesn't seem to be an equivalent in the newer mods?

simple idea for you, place a chest with comparator on it, then duct to the chest using a filter for the item u want to detect, all other items can bypass the chest if u use a restriction pipe.

I probably made it sound more complicated, really it doesn't have to be a specific item, so I could probably just use a chest and comparator anyway. I'm just surprised there isn't an obvious "emit redstone when something passes through" block.