OpenPlans is developing a reference GeoReport v2 client for the iPhone.
The idea is to support all major features of the v2 API well enough to be useful in cities that implement the v2 API, and give implementers something fun to test with.
Source code is here: http://github.com/slinkp/GeoReport-iPhone It is a fork of the open-source UshahidiiPhone app.
Issue tracking is here: http://developer.open311.org
Work to be done can be seen in this list of tickets: http://developer.open311.org/report/9