You may want to bookmark this one from Craig Ball.
“This article looks at simple, low-cost approaches to getting relevant and responsive mobile data into a standard e-discovery review workflow, and offers a Mobile Evidence Scorecard designed to start a dialogue leading to a consensus about what forms of mobile content should be routinely collected and reviewed in e-discovery, without the need for digital forensic examination.”
Craig goes on to talk in detail about the various types of information available on mobile devices, and how to include them in the eDiscovery workflow. It’s a very good, in depth, look at the topic. You could learn a thing, or ten.