The main obstacle with console development is if you want create a commercial title you must get approval from the appropriate people(MS, N, Sony) to gain a license. After that you must invest in their respective expensive developer kits. However, in the case of the Nintendo Wii, the kit is much cheaper than the others (by many thousands of dollars...I believe the Wii kit is in the neighborhood of $2000...peanuts compared to the norm).
Of course, the costs are nothing if you are able to snag a publisher who wants to release your game. They'll fork over the funding (milestones), and perhaps even for financing an engine port. For example, the 3D Gamestudio developer (jcl of Conitec) requires something in the neighborhood of $50,000 to fund a port of A6 to another platform (Mac and Xbox being examples at the time). It believe this was half, and Conitec would fund the other half. This 50 grand would have to come from the publisher, since most of us don't have that kind of money to simply given away.
Anyway, getting that approval is the key. If your title is of quality, you may get it (and with a little luck and hoodoo). Given the point & click adventures coming out on DS lately, I see that being a good place to start. However, I've heard it has memory issues; thus you aren't going to be able to go to town with the bells and whistles. Since, they're wanting to emphasize "fun" and have a reputation for being indie friendly (because of the cheap kit), the Wii may be a better fit for the advanced version of you title.
Finally, I think you can test DS games on the PC, now via the SDK. No DS unit is needed anymore (could be wrong about that).