While we don't have a dedicated iPad app (yet) Marvin is fully functional on the iPad or any other tablet/touch device.
Simply use the browser on your device to go to app.amazingmarvin.com and use the web app.
Trying out the settings
There are two ways Marvin can interpret touch events, you can switch between the two modes in the settings:
It is best to try out both settings to see how your specific device works with each. Some devices only work properly when touch events are enabled.