The whole point of making an iphone app is 1) iphone has gps 2) it's mostly, if not fully programmable 3) some people have iphones 4) therefore you can survey a site for free without a total station if you own an iphone or know someone who does, without paying for topographical data or using outdated and inaccurate databases or extracting the terrain from google earth (inaccurate too, at least for this region), and then use the points to build the terrain in Revit or any other software
If I had the resources to make it I'd probably be able to pay rent
oh. it'd only really be useful in determining change of elevation, and you can do that with a string, measuring tape/stick and level. the app would also be more inaccurate and not really a survey, but I guess relatively quick
virtually(?) every mobile phone has gps tho. you could probably even do this with a web tool, maybe it already exists