Flagging and/or Cleansing/Correcting bad telephone number data

Hoping that perhaps someone here has already been down this road and may be willing to provide some pointers.

Can anyone direct me to information regarding the use of PostgreSQL with other references to verify/flag bad telephone
numberdata? 

I've tables with 'people' data ( f/lname, addr, zip, telno, etc ).  I know that some of the records have invalid
telno's( no area  
code, transposed area code or transposed exchange digits, etc ) -- I'm looking for methods/means of identifying them,
forexample,  
'..we've used Company X's product to validate area code and exchange against zipcode/state...', '...this contrib/addon
should 
help...', '..I used http://blah.blah.com as a reference for this...', '...using software/site/data provided by X you
canautomate  
the lookup and validation of person/telno against person/telno in DB...', etc.

Please advise if there's a more appropriate forum for this also ( I realize that more appropriate may be more general
than 
PostgreSQL; at the same time I think this might be a position that many PostgreSQL users might find themselves facing
somay be on  
topic enough to warrant the email archives).

Thanks,
reid