andrelcm:
Could you share your schematic?
I ditched the latching relay and went with a standard one, but here's the schematic for the receiving device. It's actually broken into a main board and relay shield, but here is the schematic for them combined:
*Edit: First picture had incorrect wiring to the relay; fixed.
*Edit2: There is also a missing flyback diode that I'm too lazy to go back and fix
