DEI accessory

On the tilt sensor: Most alarms have a ground-when-armed output; all it does is provide a connection to ground when you arm the alarm, and open the connection when it's disarmed. That lets you control sensors and devices that you only want power on when armed. If the alarm doesn't have that kind of output, you might try simply hooking it up to the ignition switch line through a diode (for isolation when the ignition is turned on). The current draw of the sensor is so low that the ignition circuit effectively acts as a ground. Only difference is that the sensor will be on whenever you turn off the ignition, rather than arming the alarm. Don't hook the trigger input to the dome lights- That'd damage the sensor, because it can't handle the current that would be delivered through the dome light circuit. Your alarm should have a (-) trigger input, so you just need to find out which one is suitable, and tie it to that.

Thanks.  I'll go with that and post again if I run into any more questions.