%otherplayer_<player>_itemininvhasname_<name/material-name>% - Returns PNF/true/false. Can be name assigned name of item or material name that matches exactly.
%otherplayer_<player>_itemininvhasname_<name/material-name>_amount_<amount>% - Returns PNF/true/false. If amount specified is less than 1, it will assume any amount.
%otherplayer_<player>_itemininvcontainsname_<string-to-match>% - Returns PNF/true/false. Returns first match that contains provided string. Eg. Can be used to check if player has "chestplate" of any sort.
%otherplayer_<player>_itemininvgetamount_<name/material-name>% - Returns 0 or greater. Will add up multiple stacks if they match the name provided.