Hi Gordon,
This will mostly depend of the functionality of your telephony system but this can normally be easy done.
We implemented in our organization with ASPECT/UIP but implementation is mostly the same everywhere.
Mainly you will need to have your phone software grab the userid of the analyst on the phone, then call the SDM SOAP web service to impersonate that user and receive a BOPSID.
Use that bopsid to construct your URL and have your phone software push it to the screen.
As a small tip, you may also want to create a extra field in you cr/actlog tables and push your telephony call_id in the URL. This will allow you to link SDM and your telephony for reporting purpose afterwards.
As mentioned by Gordon_Preston the green book is the place to start.
/J