Well, the controller needs access to wires that serve several functions: Battery B+, Ground, Switched Ignition source, start contacts (from the ignition switch), a brake light/switch sense wire and at least one lead going to the ICM to enable the lights. (I"m probably forgetting at least one or two connections). All but the last two are available at the back of the ignition switch.

Did you DROP the underdash and look over the connections at the back of the ignition switch (or the wiring harness that leads away from the switch)? This is the most likely attachment point for all but the lights.
As Toolman says, you describe the functions of a remote start kit to a "Tee" in your opening post.