This paper presents an energy-efficient scheduling algorithm for the data-communications of soft real-time periodic tasks on multi-radio embedded devices. To cope with the dynamic fluctuation of channel conditions, a feedback mechanism that monitors radio throughput is introduced to guarantee real-time behaviors. The paper also provides a formal analysis on the scheduling, exploring the relationship between tardiness bounds and energy savings and that between network stability and (m; k)-firm deadline guarantees. This approach is applicable to real-time communication scheduling problems in which background interference and other environmental factors are not known a priori. The algorithm is evaluated in the QualNet simulator, using data measured from radio hardware.