Many wireless sensor network applications could be substantially improved if they enhance the description of the events transmitting scalar sensor data along with audio and video. For example, an intrusion detection system would reduce the number of false positives if, in addition to the alarm, the system would also transmitted a picture or video of the intruder. The problem is how to overcome the known limitations of current wireless sensor networks to support multimedia applications in terms of throughput, delay and jitter while being energy efficient. This paper presents LEMR-multichannel, an extension of LEMR for real-time applications over wireless sensor networks to address these issues. LEMR-multichannel takes advantage of the delay, jitter and energy-efficiency of LEMR, and includes an energy-efficient new dynamic duty cycle multi-channel medium access mechanism that uses the different channels available in the single transceiver device to enhance the throughput capability of the network. Simulation experiments demonstrate the superiority of LEMR-multichannel in terms of these performance metrics when compared with well-known protocols, such as LEMR, SMAC, TMAC and SCP-MAC.