Hi Hayato and Ken,
First to answer Ken's question:
I suppose I could power the transmitter from a wall-wart though the transmitter's battery is 12V and I do not think I have any wall-wart that size. However, I just tried a little experiment and it does not seem that the circuit on the receiver side remains in the closed state even when the transmitter pushbutton is held closed. I put an ohm meter across the receiver leads and held the transmitter button down, but after initially changing to show the receiver side circuit closing it quickly reverts to being open. So maybe the garage door opener idea is a non-starter.
As for the problem with signal glitches, I realize this could be a problem and agree that a more positive mechanism would be desirable, but it seems to me it would be kind of self-correcting. If the temperature set point had been reached causing the receiver circuit to be opened and a stray signal occurred to close it again the heat condition should be quickly satisfied and another signal sent to open the receiver circuit. Similarly, if a stray signal opened the receiver circuit before the set point had been reached, the thermostat should quickly call for heat again sending a new signal and closing the receiver side circuit. If the sending circuitry got out of whack and was spuriously sending signals all over the place, that would be a problem.
To try to clarify for Hayato:
I'm trying to make an inexpensive wireless thermostat that will turn a heating appliance on when the thermostat calls for heat and off when the temperature set point has been reached. I have an electronic thermostat that is currently mounted close to the appliance and is hard-wired. All this thermostat basically does is to close a circuit when there is a call for heat and open the circuit when the temperature has been reached. Because it is so close to the appliance it does not control the temperature very well so I want to move it across the room, but I would have to tear into a ceiling and wall, or run the wires on the ceiling and wall surfaces, to extend the current wiring and I prefer not to do either one.
I wanted to use a transmitter and receiver where the closing of the thermostat (calling for heat) would cause a signal to be sent to close the appliance circuit, and the opening of the thermostat (temperature satisfied) would cause a signal to be sent to open the appliance circuit. My idea was to use a transmitter/receiver that controls the opening and closing of a garage door to send/receive the signals. I chose this type of control because I had a spare one lying around. The transmitter part of the control is just a momentary contact switch, and I had thought that the circuit on the receiver side stayed closed once activated. But, from the experiment I did (see my answer to Ken above) it seems the receiver is just making momentary contact too, so that the receiver side circuit would not remain closed even if the transmitter side switch is held in contact.
Maybe I need to look into an IR transmitter/receiver.
Thanks to both of you for all of your input!
Mark