Nintendo is looking into the ability to use the 3DS to change Wii U software with Spotpass.

Coming from NWR..

Since the 3DS is a portable device, with StreetPass and SpotPass, it is possible to interact and transmit changes to Wii U without a user specifically doing so. It is not expected that everyone will go online with the Wii U, so Nintendo is looking into what kinds of changes or new data can be sent to the Wii U using the 3DS.