Well I found a module that can be set to send an X10 On when an open is on the sensor input and an X10 Off when a close is on the sensor input. So a CT-800 that gives a close when there is current sensed will send an X10 Off and when the current stops an X10 On will be sent.
I triggered my A4 addressed chime module when I opened the input to the module.
I used a Smarthome 2450 I/OLinc. Programed the X10 address in it and set it to Off at closure of the sensor input and On at opening of the sensor input.
http://wiki.smarthome.com/index.php?title=Assigning_an_X10_Address_to_the_I/O_Linc_Sensor_InputSteps 1-4.
I found with my early firmware unit. The address can be followed by the On or Off command from a HR12A Palm Pad and didn't have to be three addresses then three commands. In my test for Chime Module A4. The Palm Pad sent A4 AOff, A4 AOff, A4 AOff.
Unlike the PowerFlash. The I/OLinc can only use a closure on the Sensor Input {not sure if sensor was a real good label for it} and it can not be used with a low voltage input.
I monitored the power line and double checked the signals. I got an A4 AOff when I closed the sensor input and an A4 AOn when I opened the sensor input.
I know you wanted to not use an added power supply, but one could be used if nothing else fits your needs. Power supply through the CT-800 pulling in a 12 volt relay that has its NC connections to the Powerflash.