1. A method for prefetching sync data, comprising: downloading, to a cellular phone periodically querying a back-end server for unprocessed sync data, the unprocessed sync data destined for a plurality of mobile devices from the back-end server over a cellular network having a first data transfer rate; processing the unprocessed sync data at the cellular phone to provide preprocessed sync data; storing the preprocessed sync data in a cache in the cellular phone, wherein the cache stores the preprocessed sync data for the plurality of mobile devices; receiving a sync request from a requesting mobile device of the plurality of mobile devices; providing, in response to the received sync request, at least a portion of the preprocessed sync data stored in the cache to the requesting mobile device over a personal area network having a second data transfer rate higher than the first data transfer rate of the cellular network, wherein only a single sync request and a single corresponding response is required to provide the preprocessed sync data stored in the cache to the requesting mobile device; and erasing the preprocessed sync data from the cache only after all of the plurality of mobile devices have accessed the cache and downloaded at least a portion of the preprocessed sync data.