Just yesterday we heard that DSi-only retail games would be on the way soon. Today, Japanese publisher Alpha Unit announced the first one, Monster Finder -- though, since it was announced for Japan, we doubt it's one of the games being referred to yesterday!
Basically the only details available about Monster Finder right now are that it includes over 100 different varieties of monster and that those monsters are found with the DSi camera (hence the DSi exclusivity); and probably represented in-game by the scanner-gun thing seen in the teaser artwork. It's part Monster Rancher, part augmented reality. Monster Finder will be released sometime this winter in Japan.