It is possible for ultra wideband to penetrate human tissue, but the degree to which it does this is subject to a handful of factors. First of all, the frequency of the UWB signal and the power of the transmitter must be at the appropriate level.
Lower frequency signals may be able to penetrate deep into human tissue, while higher frequency signals may not. Additionally, the transmitter power must be high enough as low power transmitters will find it hard to penetrate deep into a human tissue.