[asterisk-users] softclient for customized apps like a call center?

[JD]

There are a variety of open source (and closed source) software-based 
Windows SIP or IAX phones out there.

However, I am thinking of using one for a inbound call center. Some of 
the things I'd be looking for:

  The ability to make/receive calls (duh!).
  The ability to 'launch' a web browser based on incoming call 
conditions. For example, launching an URL like:
       http://mydomain.com/lookupcustomer.php?cnam=xxxxxx
       BTW, I'd be happy to write the ability in myself, in which case 
the question is: is the source code easily modifiable?
  The ability to create "special buttons" for unique functions.
  The ability to make MySQL queries or HTTP queries for some kind of 
status screen? Sort of like what many of hard phones allow.
   Redundant registrations.

While I am more than willing to consider closed-source stuff, I somehow 
doubt those solutions are customizable enough.

Suggestions/Opinions?