http://ds.ign.com/articles/687/687243p1.html
Its about freaking time. According to IGN, soon the DS kiosks in stores will have multiple games which you can download and take with you.
The first demos available will be "Tetris DS, Brain Age: Train Your Brain in Minutes a Day, Mario Kart DS, Meteos, True Swing Golf and Pokemon Trozei, along with a Metroid Prime Hunters video clip."