There are many hidden items throught the game you need itemfinder to find
2 that i found today are
1 at vermilloin city use the itemfinder when you are right in front of the pokecenter. it is on the beach, i forget wat it was i think it was max ether
2. there are lots of hidden items on cycling road

also on treasur beach on 1 island 1nce a day there will be items all over such as ultra ball, pearl, and stardust

-darkone