A mobile wireless communications device may include a wireless transceiver, a series of processing modules, a shared memory connected the plurality of processing modules and to the wireless transceiver, and a memory manager module for generating respective data location indices for data stored in the shared memory. The processing modules may cooperate with the shared memory and the memory manager module so that an upstream processing module stores given data in the shared memory, and so that a downstream processing module receives the data location index for the stored given data and processes the stored given data based thereon. The device may further include a security module for selectively purging data from the shared memory.