Almost every mobile app developer has to fetch (or update) data from a remote server via remote APIs. The mobile app under development is tightly coupled to a) the existence of these remote APIs, b) the stability/reliability of the APIs, and c) the types of data that is returned from the APIs.
Unavailability/unreliability of APIs leads directly to a significant loss in developer productivity. Insufficient test data being returned from the APIs also reduces overall product quality (for example, it is difficult to test how the app reacts to various response codes and data conditions).
Yesterday, I released ServeUp App – a Mac OS X application that can be used by iOS and Android developers to serve mock responses to iOS or Android applications.