This is a nice idea, and would be useful to those in this particular niche (such as myself), but it is a small market if you just look at the architects. Also, it is more complicated a task now as most of the industry that is forward thinking (and thus potential customers) are using BIM (building information modeling), primarily Autodesk's Revit.
So to make it a vastly bigger market, to include all the construction participants including architects, engineers, contractors, subcontractors, you would need to make the app access the BIM model and be able to attach data to it. Revit has an SDK, so with a great deal of difficult work, an app could be made. Of course, a launch date around 2010 may be the best plan given the largest reduction in Construction that I've ever seen recently.
Update: I just realized that there is a growing movement in the construction industry called Integrated Project Delivery which is basically lean management applied to construction and involves the intense collaboration of all parties in construction. To that end, there are now a growing number of online BIM integrators where different participants can share in real-time their different BIM applications. So the iPhone app may be much easier than I thought if you can access into the online BIM data, say, with a REST api.
The availability of inexpensive hardware and AJAX is a powerful enabler once again, combined with high speed mobile networking. Publish all of these applications you propose as web applications, with a "tablet" mode -- actually several "tablet" modes each tailored to different screen form factors.
The economics of the US construction industry as a whole involve freaking huge numbers! Very low-cost applications (don't forget corporate licensing) that become a "must have" can make someone a billionaire.
(And yes, there are industries where certain mobile apps have become "must haves." ePocrates was one such app in the old Palm days. Don't know if it's still that way, though.)
So to make it a vastly bigger market, to include all the construction participants including architects, engineers, contractors, subcontractors, you would need to make the app access the BIM model and be able to attach data to it. Revit has an SDK, so with a great deal of difficult work, an app could be made. Of course, a launch date around 2010 may be the best plan given the largest reduction in Construction that I've ever seen recently.
Update: I just realized that there is a growing movement in the construction industry called Integrated Project Delivery which is basically lean management applied to construction and involves the intense collaboration of all parties in construction. To that end, there are now a growing number of online BIM integrators where different participants can share in real-time their different BIM applications. So the iPhone app may be much easier than I thought if you can access into the online BIM data, say, with a REST api.
http://en.wikipedia.org/wiki/Integrated_Project_Delivery