I've always thought it was cool when games used peripherals to interact with real life objects or aspects and somehow use it in a gameplay context. I thought I should list some cool examples and maybe hear if you know of any as well.

Barcode Boy (http://superfami.com/barcodeboy.html)


Barcode Boy was this Game Boy RPG that came with a barcode reader and would allow you to translate the barcodes of products you've purchased - like food and toys - into in-game equipment, stats and items. Apparently there was a big problem in Japan with kids going into stores and ripping off the barcodes of food products so they could convert it to in-game stuff. I wish there was a YouTube of this game.

Treasure World DS

This is sort of a Pokémon-esque game that looks up nearby WiFi connections and store unique data that, in the same way as Barcode Boy, is translated into in-game objects. These objects can be used to decorate your character or your personal space, also known as your "Garden", which also doubles as a step sequencer that can play music based on the arrangement of your objects. There is no real gameplay, so I think the main draw of this is sitting on the bus and seeing what kind of cool stuff nearby WiFi connections will generate, and sharing the best spots with your friends.

Ghostwire

This is a collection and adventure game where you use your handheld's camera (mobile or Nintendo DS) to find ghosts in your surroundings. The objective is to communicate with them via your DS and help them with their ghastly problems so that they can finally find peace.


I also found this cool iPhone 3GS game some time ago which was basically a zombie shooter where you were able to rotate your phone in a horizontal 360 degree in order to shoot incoming enemies. I can't remember what it was called though.

Wow, Robopon is not even just a Pokémon clone, it's a complete knock-off down to the name, gameplay, menus, sprites and game tagline.