Capacitive touchscreens are not ideal tools for 3D modeling. Unless you have an active digitizer and stylus, or superhuman patience, or preferably both, the amazing models on display in the screenshots below will probably be unattainable in the new 123D Sculpt+ app. But that doesn't mean it's not fun to try out a tool that, at least on a technical level, has a lot in common with professional 3D modeling programs.
The idea behind MONZO, a sort of simulator for Revell-branded plastic model kits, is actually pretty cool. You "open" a kit, read through a paginated, simplified version of the instructions, then "assemble" digital analogs of the real pieces from the kit. The 3D model of the, uh, model is extremely detailed, and the pan and zoom tools let you examine it minutely. If your phone or tablet has decent 3D capabilities, it's a surprisingly soothing experience.
Today, Autodesk announced Maya LT, a streamlined 3D modeling tool targeted at independent and mobile game developers. The maker of AutoCAD and 3ds Max is looking to make a splash with developers by introducing a lower-cost version of its Maya software, but still keeping it equipped with powerful animation tools, including a skeleton generator with the capability to calculate inverse kinematics (using Autodesk HumanIK), and a viewport preview system to visualize models as they would appear in game with full lighting and texture effects.