(via water cooler games) Gaming-Age Foruns has a post on DS Brain Training for Adults, the forthcoming non-game for the DS. The screenshots are in japanese, but they give a good general impression of the product.
Maybe because it is "for Adults" (and maybe because it is brain training), it does not have distractive colourful game-like graphics (except for the polygonal doctor head) - a major difference from the PSP's Talkman, which is also more like an application than a game (Nintendo will also release a Japanese-English dictionary, so let's see how they compare).
Brain Training for Adults, as the name suggests, might be Nintendo's move over an older audience. Not only older than the average Mario and Zelda's fan base, but even more. Not young adult, but 'adult-adult'.
Apparently, Nintendo's approach to the market right now is trying to give make games for everyone (and not only games rated as "Everyone" by the ESRB), and the puzzle-magazine style of Brain Training might help.