With Apple's launch of iPhone 5 came several improvements to iPhone's camera. One of the most useful for commercial real estate could be iPhone 5's "iSight" panoramic photo abilities. I am not sure that, in its current state, the feature is a complete replacement for an app like TourWrist, but it is an alternative for sure.
What's even better, is that this capability will soon be a part of iOS 6, which means this feature will also trickle down to iPhone 4S.
Now get out there and use it!