Key to blender is workflow. Make the creative connections get the workflow. In the appstore compatible apps incorporable to such a workflow include the 123D suite, Air login, 3D Portfolio, or Osc to midi via such things as Touch OSC. More interesting and pertinent could be a webcam to blender interface overlay. Minority report here we come!
123D Sculpt, 123D Creature, 123D and 123D design each do exportation of .obj or similar filetype. Look in the appstore. Several 3D portfolio apps exist able to import and display .obj or similar. Also wireless login toos open up the possibility of touch interface for all of blenders toolset from the Ipad or Iphone. For more hardware control staying within the iPad, purchase a wireless or bluetooth keyboard for the Ipad, (many models exist, your choice). Blenders key interface is customisable, as such and program able to send key combinations from OSC or MIDI data is able to control blender functions. You could if you so chose control all of blender from musical audio input. Sounds like a thesis topic to me though. Back to topic, OSC ipad apps usually have a keyboard layout.
Halfway down Touch OSC's software page is a downloads section to the Touch OSC editor (definately free) and OSC bridge. Figure out exactly what you need from Blender and the workflow becomes more obvious as to how to adapt your workflow.
More things, Blender's tutorials section includes links somewhere to users migrating from Maya, completmenting this is CameraMan™ for Maya for Ipad. Oficially the appstore details say that the app is for Maya however they also say the control panel scripts are cameraman.py control panel scripts. There is also in the appstore for Ipad autodesk products and AutoCAD products.
Also apps such as Sketchbook Express could all connect with Blender. (texture map editing in sketchbook suite)
Or something such as iFontMaker, able to export created font files. Something a simple Blender ported for Ipad would not contain as Blender for OS does not export to .TTF files, however does READ .TTF files.
Each of these could definately compliment a Blender Workflow. Have you found something from this helpful?