I have been actually researching into this.
It wouldn't be like fully Blockland itself, but a miniature build builder thing.
In theory, you would be able to construct the thing on the ipod touch and then save it, perhaps uploading it to a main server or something, and then use it in the full version of Blockland.
I am sure I could do at least the building part if Flash for the iphone actually happens (given a rather long time frame to work as well), but I would have no idea how to go about the saving of builds or, much less know of the connectivity to such an upload server.
(Also I have no idea how I would get the special shapes like trees and stuff to work)