Advantages of remote health monitoring are incontestable: prolonging the patient's possibility to stay at home by monitoring the health condition remotely, the quality of patient's life is improved as well as healthcare costs are significantly reduced. Parkinson's disease is one example, for which some wireless monitoring systems have been presented recently. However, concrete performance evaluations for the IEEE 802.15.6 standard based communication in the realistic use scenarios have not been presented yet in the literature. The aim of this paper is to evaluate performance of ultra wideband energy detector receivers on the physical layer of the IEEE 802.15.6 standard. The monitoring system and node locations are designed for monitoring Parkinson's disease symptoms. Measurement based radio channel models were used in the evaluations. Two modulation methods, on-off keying and pulse position modulation, are evaluated and compared using two different antennas suitable for body area network communication. Pulse position modulation based system is found to outperform on-off keying based system, which on the other hand, is simpler to implement. Furthermore, it is shown how antenna placement, position, and properties are impacting on the channel characteristics of the radio link, and hence, on the bit error rate performance.