Is the sound "ř" unique to Czech?

The Czech raised alveolar trill that is represented by ř in Czech orthography is phonetically quite unique. However, there are apparently certain Polish dialects where it exists as an allophone of 'rz' (See this listing on Wikipedia). This resource on Polish dialects (in Polish) gives a distribution of these dialects and suggests that the full realization is only sporadic and present mostly among the oldest speakers. I'm not sure of any detailed study that has looked at this from a truly contrastive perspective, though.

Although the prototypical phonetic instantiation of ř is voiced, it has a voiceless allophone which is acoustically quite similar to the Polish 'rz' sometimes leading to claims that Polish has the 'ř' phoneme.

Czechs are taught that 'ř' is unique to Czech (and some other little known language in Papua New Guinea) but again I don't remember seeing any study of this other than anecdotal evidence. Speech impediments related to the sound are called 'Rotacismus Bohemicus' suggesting that this may be a peculiarly Czech sound.