Man this topic is exactly what has been on my mind lately. Here are my thoughts (94 SE).
I know the SE has some sort of alarm built in. It has the dead lock function that sets the little red light on the dash. But also you can just push the plunger down, or turn the key 15 degrees to lock it without setting the alarm. I have had mine go off, and it is just basically flashing lights and horn. Now, I am worried somewhat on if it will be possible to integrate a keyless system in with the locking system. My thoughts are that the locking or unlocking mechanism is always initiated by a mechanical movement. I am not certain what would happen if you just put some juice across the solenoid. (what worries me is this, on my Mazda, if you are inside, and you lock the doors and give it a little time, the factory alarm will set. If you unlock the door manually, (moving the mechanism by hand) and then open the door, the alarm will go off. If you unlock the door with the button, then open the door, all is well. Weird huh? That kind of black magic makes me wonder if wiring up the solenoid in the saab will work)
Here is what I am thinking about doing, I bought a power door lock actuator from parts express.com for 4 bucks. I am planning on puling the door panels soon, and putting in new speakers, and I will investigate a little more on what it will take to electrically add keyless entry. If I think that will be unsucessful, I am planning on adding my solenoid into the door to mimick the pushing and pulling of the plunger. I have used these before with good sucess, so I know this is a surefire way of getting it done. Hopefully if won't be needed, and we can just wire it in. I will know more in a week or so when my parts arrive!
Tboy