Digital Watch
Comes with the Poketch.
Calculator
Comes with the Poketch
Memo Pad
Obtained in Diamond, Pearl, and Platinum from the president of The Pokétch Company after obtaining the Coal Badge.
Pedometer
Comes with the Poketch
Pokemon List
Come with the Poketch
Friendship Checker
Obtained in Diamond, Pearl, and Platinum from a woman in Eterna City's Pokémon Center once Team Galactic has been defeated in their building.
Dowsing Machine
Obtained in Diamond, Pearl, and Platinum from Dawn/Lucas upon arriving at the Route 207 entrance to Mt. Coronet (Platinum),
Berry Searcher
Obtained in Diamond, Pearl, and Platinum from a girl in the Berry Master's house in Route 208 after answering "yes" to her question.
Day Care Checker
Obtained in Diamond, Pearl, and Platinum from a man in Solaceon Town's Day Care.
Pokemon History
Obtained in Diamond, Pearl, and Platinum from a man in Solaceon Town.
Counter
Obtained in Diamond, Pearl, and Platinum from the Veilstone Department Store at the counter on the second floor.
Analog Watch
Obtained in Diamond, Pearl, and Platinum from a resident of Celestic Town.
Marking Map
Obtained in Diamond, Pearl, and Platinum from the president of The Pokétch Company after obtaining three Gym Badges.
Link Searcher
Obtained in Diamond, Pearl, and Platinum from the president of The Pokétch Company after obtaining five Gym Badges.
Coin Flip
Obtained in Diamond, Pearl, and Platinum from a guest in one of Hotel Grand Lake's suites by Lake Valor.
Move tester
Obtained in Diamond, Pearl, and Platinum from the president of The Pokétch Company after obtaining the Icicle Badge.
Calender
Obtained in Diamond, Pearl, and Platinum from the president of The Pokétch Company after obtaining the Icicle Badge.
Dot Artist
Obtained in Diamond, Pearl, and Platinum from a Pokétch developer by Pokémon Rock in Sunyshore City after showing to him a Pokémon with a naïve nature (Rock Climb is required).
Roulette
Obtained in Diamond, Pearl, and Platinum from a Pokétch developer by Pokémon Rock in Sunyshore City after showing to him a Pokémon with a naïve nature (Rock Climb is required).
Trainer Counter
Obtained in Diamond, Pearl, and Platinum from Professor Oak upon entering Pal Park.
Kitchen Timer
Obtained in Diamond, Pearl, and Platinum from a girl in Pal Park's lobby after showing a Snorlax to her.
Color Changer
Obtained in Diamond, Pearl, and Platinum from a girl in Pal Park's lobby after receiving the Kitchen Timer, then returning and showing a Kecleon to her.
Matchup Checker
Obtained in Platinum by the entrance of the Great Marsh after catching five Pokémon in a Safari Game.
Stopwatch
Obtained from a Nintendo event.
Alarm Clock
Not in Platium
Obtained in Diamond and Pearl from a Nintendo event.
Source