Hopper to trigger say command for each item inserted?
You can reset the transfer speed of the entry hopper for each segment (just below the top row of hoppers) so that the comparator has enough time to reduce in strength before the next item passes through. Keep in mind that this will slow down the sorting mechanism by at least 4 game ticks (2 redstone ticks). Image example:
The command would target the hopper circled in yellow, adjusting coordinates as needed:
/blockdata ~1 ~4 ~ {TransferCooldown:4}