Hi, is it possible to check to see what relays are closed (or opened) by sending a bluetooth command to an arduino controller? (to check for that?)
You would need circuitry to detect if the relay is opened or closed. However, yes, it is entirely possible. In a product I've worked on, the relay was DPDT, and I only needed one side of the relay for the product, so I added a Pull up resistor connected to an uC pin (Not an arduino, but it would work exactly the same), and then connected the Normally open side to ground, so that whenever the relay closed, the signal got pulled down. As long as you can do something to detect between the open and closed relay, you should be able to then interface it with an Arduino with a bluetooth shield.
Plan B;-
Stick a hall effect sensor by the relay coil to sense the magnetic field when it is energized.
Ok, It's possible but maybe not practical for this arduino audio sketch I'm working on.
Thanks.