Latching relays with Arduino

I am trying to do some home automation and turn my lights automatically. My light switches run only 2 wires, so no neutral, making it unfeasible to put a relay on the switch since it would require powering the Arduino, etc. One idea I had was to have an Arduino Nano running on batteries on the switch. In order not to run out the batteries in a week, I would have a latching relay that would only draw power when it switches on or off. Then the Arduino would go to sleep and wait for an interrupt to do anything else.
My understanding is that the relay would stay in its position and would not waste battery. Questions:

  1. Is this feasible?
  2. Is there a latching relay that can work with Arduino in this fashion?