Single-card multiplayer and the possibility of demo games and interactive movie content.
During his speech yesterday in Japan, Nintendo President Satoru Iwata spoke about several concepts of the wireless functionality of the DS.
He began by restating the DS's capability of playing multiplayer games with only a single game card:
"The DS's wireless connection isn't just a substitute for the link cable that was used on the Game Boy. The DS has wireless download capability, which allows it to receive a program and to execute it. With it, people can play games together using only one cartridge."
We've known about this feature for some time now, but Iwata also mentioned that the same technology could be utilized in other creative ways:
"Although this won't be available at launch, we're thinking of using the wireless download function to change the way in which people try out upcoming games at retail outlets.... We're thinking of a system where people can download a demo program, with a time or a usage limit, to their own DS. We hope that this system will allow new potential hits to be recognized by everyone, and that it will help to buck the trend where only sequels are hitting the sales charts."
Following up on Yamauchi's recent comments that Nintendo should begin an animation studio, Iwata confirmed that the company is considering the idea, but that it is too early to give any more details on the subject. Instead, he segued into introducing the concept of tying downloadable DS content into movie theaters (I suspect you'd need to keep the volume down):
"On a related subject, we're planning [to] try integrating the DS with movie theaters. By using the system's wireless functionality, users that bring their DS and GBA Pokémon cartridge to designated theaters will be able to download game data that will be distributed during certain scenes of the next Pokémon movie. In one scene where the main characters meet a new Pokémon, that character's data will be sent to their cartridges. This will be the first time such a distribution scheme has been used anywhere in the world."
And finally, the example he uses for this idea is none other than a GBA game. We can only conclude that this means wireless GBA games are also compatible with the Nintendo DS's wireless technology, which may have something to do with why the GBA wireless adapter only works with games programmed for it.