The Nintendo 3DS keeps getting better and better, and the newest system update is no exception. Version 7.0.0-13 adds the ability to connect to the Miiverse, and link your Nintendo Network ID to access a unified wallet for the Wii U and 3DS. When logging in after the update, double and triple check that you enter your information correctly, as the system can only link to one account.
This is the first step to having a real, fully connected account, but Nintendo still isn't quite there yet. With no ability to Cross-Buy Virtual Console games that are on both systems, you need to purchase each game twice to play on the Wii U and 3DS. Also, Nintendo hasn't clarified if you still need a police report to get your games back if your 3DS is missing or stolen.