I've tried both the Motorola HS810 and the Treo bluetooth headsets, and this by far is the best one. The problem with Motorola is that it doesn't synch with the Treo 650 100% of the time; while the Treo headset has very poor volume (I need to be in a quiet room to hear anything). The Cardo Scala 700 has great fit (it sits right over the ear canal), great volume (even when driving with windows down), and it synchs with the Treo 650 all the time. This is the headset I'd recommend for anyone with the Treo 650.