Rick, do you have any idea how much current that relay draws when it's in its quiescent (off) state? Could your box last for, say, 6 months as long as the buttons weren't pushed?
Also, you mentioned the ability to use the button as both a power switch and an input to the Arduino, but I gather the circuit you share above doesn't show the latter? If you wanted to add this, I guess you'd just connect the relay pin 1 line (from the button) to an Arduino digital input?
Thanks! This is good stuff.
Mikal
It doesn't draw any current. The latch relay is like a switch that is operated by magnetic coils. When it's off there's no connection between pin 2 and 3, so no current flows.
You can connect pin 1 to the arduino to use the pushbutton but if you do so you should add a clamping diode between pin 1 and 5 like on the other side. You need that because there is a short spike of energy with reversed polarity in a relay when you cut the power to a coil. That could damage your Atmega chip without the diode.
If you try this o a breadboard start by applying 5V to the relays coils (Pin1&5 and Pin6&10 in my schematic). You should hear the relay clicking if you put power to the alternate coils. Then check the resistance from pin 3 to pin 2 and 4 and you'll see how it works.
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BTW: Thanks for the tinyGPS library! I used it in this box 
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