MyDoorOpener.com

I'm going to use MyDoorOpener to control driveway gate. I have a gate operator by DoorKing. I currently have a keypad that opens the gate. The keypad can either open or hold open the gate. To open the gate, the keypad just completes the circuit momentarily with one code. We use another code to hold open the gate until we want it closed. If I connect a wire from the relayshield on the Arduino to the same terminal at the gate that the keypad is connected and the keypad is used to hold open the gate I will be getting current back on the relayshield right? Will this damage my relayshield or Arduino? The reason I want to connect them to the same terminal is so that I can use the openNotificationsHandler to notify me when the gate is opened by using either the iOS app or gate keypad. I'm assuming that this would fire if the keypad completes the circuit and I get current back at the relayshield?? I don't tinker with circuitry too much so any advice would great. I can't really install a limit switch to accomplish this because I don't want to run another wire from the relayshield to the gate operator (distance is really long).

Why don't you use CAT5 cable between the Arduino and your gate operator? That single cable (cheap $)
typically contains 4 pairs. So with a single cable run, you'd have more than enough wires to accommodate
current and future needs.