Virgin et al
I started a thread on this about a year or so ago after hearing a programme on the Beeb about their use in Japan.
I have tried searching for the original thread again but with the search facility in it's present state, no joy. The details are that they are available mail order in the UK (and elsewhere) at about 100GBP. They are NOT (as far as I know) illegal, and they pose no threat to the emergency services since they do not affect pagers. The operating range is about 50 metres so it deals quite nicely with the verbal diarhoea addicts and are installed in some concert halls to deal with the prats who can't cope with sensible social behaviour.
The information in the original thread was kindly provided by Ex Sim Guy and, if he is still with us, perhaps he could repeat the URL for the e-mail source.
So far, my IQ (irritation quotient) has not quite reached the £100.00 mark but it's getting there !!