Now that’s a very interesting surprise! After releasing a rather useless “Fluid” application (actually a technology preview) on the iPhone a while ago, Autodesk this time released a winner. SketchBook mobile is a nice sketching application. Other than most similarly-minded iPhone software, it has nice brushes and even boasts a layer system. Here is a more detailed list of features:

• Multitouch Navigation
• Double-Tap Corner capability
• Over 20 Brushes
• Synthetic Pressure Sensitivity
• Dynamic Resizing
• Customizable Brushes
• Gallery
• Save Work-in-Progress
• Directly Email Pictures
• Import Images from Library or Camera
• Full Palette of Colors
• Interactive Color Wheel
• Store Custom Colors
• On Canvas Color Picker
• Landscape and Portrait Symmetry
• Layers with Reordering and Merging capabilities

Autodesk's mobile Sketchbook app

Background images can come from either the photo library or (for iPhone users) can be taken with the internal camera. This should be a great feature if you want to take a picture of a plan and start sketching over it right away. It would be nice if the user could email an image that preserves all layers, though – I haven’t seen that feature yet.

P.S. On a more frustrating note: I recently updated my iPod Touch (1st generation) to the 3.1 operating system. That move apparently removed my capability to attach an external microphone. Very annoying indeed! It is not good practice if a company removes a feature that I paid for. I’ll likely downgrade back to 3.0 after this (and I’ll put Apple into the same category as Microsoft from now on).