Hello, I am one of the developer of Sketches. I can confirm that our application runs both on the iPhone and on the iPod touch. You will need to jailbreak it, though. This is because no official support from Apple for third party apps exists yet, although it has been announced that a mechanism for developers to distribute their apps will be unveiled in late February.
If you do decide to jailbreak your iPod, the easiest way to install Sketches is using Installer.app (http://iphone.nullriver.com/beta/), an application that will allow you to download packages over your WiFi
connection. Sketches is listed in the Productivity section.
Thanks a lot for your interest in our software.