Hi I am looking to control a security system with a pc What I want to do is;

I have an existing alarm system, detects normally open and closed circuits, will alarm on changes in those conditions and will activate a relay and open and close another circuit, switch 12 volts on ..etc the usual alarm things.

I also have two ccd cameras and microphones on ir sensors on these (normally closed).

I also have a PC with video capture card, modem and sound card.

What I plan to do is two fold, and are separate events.

Event 1
Alarm activated.
This condition triggers a circuit to close. What I want it to do is trigger off my pc to ;
1. register the event, write to a log file.
2. Dial a preset mobile phone number... and send a sms message to that number.

Event 2
Motion Detected
This condition opens a circuit. What I want it to do is;
1. register the event, write to a log file.
2. switch the video input to the correct camera then start video/sound capture for a prescribed time.

Who can point me in the right direction in the steps of;

1. External to the PC, detect a change in state of N/C, N/O circuits (three separate circuits)

2. Respond to the detection of 1. by running a program

3. Switch an external relay input. (switch the input of the camera from one to the other depending on which sensor detected the movement.

Hope that makes sense

Adam