Does anyone know if those room bark control devices like this one:

http://www.ultimatebarkcontrol.com/

or

http://www.securepets.com/pbc1000.html

Are they effective? We will be moving in the near future and I some of the nice places we are looking at are duplexes, We don't want the dogs barking if we are gone, if they do, to bother the neighboughs. And we are not a huge fan of the no bark collars.
Nicole