The UPISketch Development as part of the even "urban music boxes and troubadours" goes on:

Since the first target is a touchscreen device, the navigation will be simplified with the use of two-finger touches for zooming.
You can draw details at any scale and have the playhead updating the page at current zoom level.Finger touches are monitored for debugging purpose.
This is running on a Iphone5s with screen sharing activated, so not very responsive.