I would like to programmatically access an STK (SIM Application Toolkit) application without using my handset. GSM modem and/or handset is attached to my PC via USB and/or R
While I have not worked directly with SAT/STK myself, I can give a little information to where you can read more. The wikipedia article contains some information and pointers and the GSM 11.14 standard is available here.
This discussion thread contains some practical information.