I can't move widgets in the dashboard in Safari on iPad3. This might be a bug.
I can move simply the widgets with the mouse in a browser on the desktop mac.
I don't use the Piwik app on the iPad.
Thanks for the report! see also: #5029
I wouldn't consider tablet as mobile. On a tablet, when opening Piwik, you usually wanna see the kinda regular view. So this ticket would be about "Make theme work on touch devices"