i have used the HeartMath emWave2 monitor. it was recommended to me by my neurofeedback practitioner while i waited to start NFB (i had an assessment with him and it was going to be four weeks before i could start sessions due to his holiday and scheduling). so he recommended i start using the monitor and tracking my coherence to help reduce my stress levels and get some better sleep. i believed it helped a little with helping me to calm my anxiety and i did sleep a bit better, but the relief from it was nothing compared to doing NFB. plus as soon as i started doing the NFB, i stopped using the monitor. so my results may have been better if i had used it longer.