where to find heart poketch

[Poffin]

where do i get hearts poketch?

[Pika22]

#06 Friendship Checker
A very useful application that you get early in the game. All the Pokemon in your party are displayed on the screen, bouncing around. By placing the stylus on the image of a particular Pokemon, it will show its affection/friendship/happiness level with a simple scale: 0 Hearts means its indifferent or simply doesn’t like you, 1 little heart means it cares, 2 little hearts means it likes you a bit and 2 Big hearts means it really like you.

Obtained: In Eterna City Poke Center, talk to the Girl closest to the door.

see here:

Pokemon Platinum Poketch Applications Guide

good luck in obtaining and using all the poke apps!!!