I have 2 of them... mach 1 and mach 3. They are a lot of fun and the jokes are really corny! however, when they send out a purposeful transmission about wait times and such, it's a real joy to have.
Originally the plan was to install the system in DL, but it did not prove to hav ethe appropriate guest interest ratio to cost investment in WDW. The plan was then scrapped.
They are now extinct - they don't sell them anymore - although you can still use them in WDW. They are now playing with Nintendo DS technology in WDW as an information and game alternative.