Easy.
First you have to defeat the elite four in the Pokemon league, and have the national pokedex. once you have done all these you will have to go past Route 219, 220 and 221, this will lead you to a building called Pal Park. enter this building and Prof. Oak will talk to you. he will then give you the Chaining app.
you know where you get the poketch, well for every badge you get the owner gives you one more app for it. i think you get it there. if not, try talking to everyone in solocean town.
a daycare checker is an app on Pokemon diamond and pearl. It lets you see what 2 Pokemon are in daycare and lets you see what level they are.
Talk to the dude at the Poketch place in Juibilife City. It should be simple it is a small building with 2 doors.
Get the PokeMarker Poketch app from Jublife City Poketch building. It will show you where Mesprit is.
in the entrance to the great marsh in Pastoria talk to the cowgirl then go into the great marsh and catch 5 Pokemon then talk to her again and she gives you the app
after you've completed sinnoh dex+Pokemon league,you talk to dawn who should beoutside professor rowans house.you might have to talk to her more than once.it is not called chaining app,its called poke radar,hope it helps!!!! ^_^
Eterna City's Pokemon center. Some random dude gives it to you.
In jubilife city.
on the touch screen after you receive the app.
you come with it!
It makes the Pokemon you tap 'cry'.
you get it from a person in Solacean town.
get the Poke tech App Poke happyness
The Pokemon Diamond and Pearl series can be watched on the official Pokemon TV website or by watching them using the Pokemon TV app for iOS and Android. You can also download the Diamond and Pearl episodes legally through the Pokemon TV app, but only up to 3 episodes at a time.
its included in the default applications
You get it from a women on 1FL of the Pokemon Centre in Eterna City.
use the dousing app. around the lobby