I have an actual DS, so I don't need an emulator. The only game I played on an emulator was Pokemon Emerald. The reason I played that on an emulator is because I did not have a gameboy advance or any money to buy games. I'm not sure if there are any working DS emulators. There is one called the DeSmuME Emulator, but I don't think it is working yet.
Do you mean the wii shop channel? You, have to have a wireless router and you need Wii points in order to purchase games. I've never used it because I have a lame internet connection and it would take forever to download.