Can you use a appliance module. A 120 volt AC relay and a manual reset button or do you want an all in one thing?
You could use an applance module to supply power to a 120 volt AC relay but wire one side of the coil through a set of the relays normally open contacts. The the normally open Reset push button also across the same relay contacts.
If the appliance module is On. 120 volts is available to power the relay but it will not turn On until the reset push button is pushed.
After the relay is On. It stays On through the now closed set of contacts of the relay.
If you turn Off the appliance module the AC is removed and the relay turns Off.
Turning the appliance module back On does not pull in the relay until you again push the reset button.
A second set of relay contacts could be used for anything you want.
Brian,
Sounds logical and a possible solution.
First, let me modify the requirement: 24 VAC max and low current.
Here's another possibility:
Use a NC magnetic security switch at the bottom of a cylinder with the 24 VAC load current passing through it.
Suspend a magnet over the cylinder with a 24 VAC electromagnet holding it in place.
When you send a signal, the 24 VAC and the electromagnet are both de-energized and the magnet is released to fall onto the switch.
If another X10 ON signal comes along, the 24 VAC transformer will energize but the load will not have power.
The magnet must be manually lifted away from the magnetic switch to reset the system.
http://www.coolmagnetman.com/magacem.htm