We investigate power allocation strategies for distributed decode-and-forward (DF) parallel relay networks. We first propose a distributed decision mechanism for the relay nodes to make decisions on whether to forward the source data. Specifically, we identify the optimum distributed power allocation strategy that minimizes the total transmit power while providing a target Signal-to-Noise ratio (SNR) at the destination with a target outage probability. We also consider two simple distributed power allocation models, where the source does not contribute to the relay selection in the first model, and single relay is employed in the second model. Simulation results are presented to demonstrate the performance of the proposed distributed power allocation schemes, and the considerable power savings they provide with respect to random relay selection.