The previously reported STELLA Modeler for iPad is here from isee systems, maker of iThink / Stella.
The interface is optimized for touch and it seems to be the easiest way to create System Dynamics model on a tablet. The iOS app is available to download STELLA Modeler for iPad from the App Store for $39.99.
The fully featured app can create, run, and share models made with STELLA or iThink v10.
Here are some tutorial videos for Stella Modeler for iPad:
Exploring results: 80 seconds
Model settings: 3.5 minutes
Using graphical functions: 6.5 minutes
How to build a SD model using STELLA Modeler for iPad: 20 minutes