To answer your question, the best way to do this is to set up a comparator with the /clear command (i.e. /clear @p [insert block id of item here]) and a redstone clock and a comparator attached. What this does is it tries to clear that specific item from the player's inventory. If it succeeds, then the comparator will activate the redstone (if you want to give the item back, just add another command block on the line with /give).
if u knew
thx
ELEMENTALS UNLEASHED MOD
http://www.minecraftforum.net/forums/mapping-and-modding/minecraft-mods/2355420-e-l-e-m-e-n-t-a-l-s-unleashed-as-good-as-elementsAre You Ready for the Necromancer? Click Below to Find Out...
http://www.minecraftforum.net/forums/mapping-and-modding/maps/2289723-necromancer-boss-fight
BLOCK NINJA
http://www.minecraftforum.net/forums/mapping-and-modding/maps/2348266-1-8-block-ninja-the-game-remade-revision-edit