Data from two different news readers for iOS -- Zite and Flud -- shows similar usage patterns that follow predictable cycles throughout the day. During the day, users are more likely to access the apps through their iPhones, and they only stay engaged for a few minutes. In the evenings, users break out their iPads and spend much longer amounts of time with the apps. In addition, the apps experience a surge in use around mealtimes.
For mobile development pros, the takeaway is to build two separate versions of apps. The iPhone version should be geared for short bursts of activity, while the iPad version should encourage longer periods of involvement.