There's a lamp in my son's room that we use for reading and the bedtime process. I'd also like to link it to a relay connected to a Particle Photon that we could signal him down for dinner with. But I'd like both methods of turning the lamp on and off to work independently of each other. Is this possible?!
Assuming that you have SPDT contacts on your Particle Photon, you can wire it up the same way as a 3 way switch. One of the switches would be the physical switch in the bedroom, and the other one would be the remote controller switch in the Particle Photon.
When you change either switch, it changes the state of the lamp. If it was on it turns off, and vice versa. When you "blink" the light with the Particle Photon, if will blink ON/OFF if the light was off and OFF/ON if the light was on.