With the introduction of the Nintendo DSi came the announcement of DSWare games. Essentially this is the DSi equivalent of WiiWare titles (if that wasn’t obvious enough by the name). To pay for this, you’ll need Nintendo Points (which are re-branded Wii Points). You’ll buy the same cards that you’re getting now for your Wii, but instead you’ll be able to load up either console with points. The real question is whether or not you’ll be able to transfer points between the DSi and Wii.
Unfortunately, the answer is no. If you load up 1000 points on your DSi, and want to buy something for your Wii, you’ll need to go buy a new card. I’d like to think that Nintendo was capable of coming up with a better solution, but for all of their innovation on the Wii, they’ve been a bit behind on things when it comes to online capabilities.