Although I haven't actually used it, I've seen pictures of the WWDC 2012 app in which it appears each workshop was given its own location on an event map. Is this simply a UIImage with a pin drop?
I also found this local mapping startup: http://gigaom.com/mobile/wifarers-mobile-app-doesnt-just-map-the-indoors-it-maps-the-objects-within/
The total number of venues at WWDC is always pretty small -- perhaps around 20 including the labs. And there are only three floors in Moscone West. You could certainly do that sort of map with a set of three images and a pin superimposed in the correct location for each venue. That seems like the simple solution.