Sorry, I realize that I wasn't very clear, I was trying to get it posted before I left to pick up my daughter and rushed it.
I'm interfacing a Moteino with a commercial product. 95% of the time I expect the Moteino to be sleeping. 95% of the rest of the time, the Moteino would be monitoring this signal, reporting any change from high to low back to the gateway, indicating that an event has taken place. Infrequently, I would like the Moteino to be able to initiate the event - pull the signal low.
Let me use the GarageMote as an example. I realize that GarageMote may have a different method for initiating a door open or close, but lets say I want to know if/when someone pushes the inside button to open the garage door. That 3.3v signal comes out of a pin on a micro-controller in the opener, connects to a N/O push-button switch and goes back up to the controller and ties to ground in the opener. I put a Moteino next to that switch tie the ground to the Ground return line and monitor the 3.3v line. Vast quantities of time sleeping, occasional reports to the Gateway: "Hey! Someone just pushed my button!" And, on rare occasions, when I'm laying in bed and see that the door is open, I can send a command to my faithful 'Mote, "Tie that pin to ground for 5 seconds for me, little buddy, will ya?" And smile as I watch the door descend.
I'm probably over thinking this. On one hand its probably not a big deal. But I can't measure that current inside the chip, and I don't want to wind up with a dead pin, and not know it.
LG