I'd be very happy with a 1.5v version especially if would make it cone out sooner. I assume you would sell this from Seeedstudio.
I have a situation where my gfi occasionally trips in my workshop. There are some things in there that can't go long without power. Beer fermentation chambers, cooler for beer and taps, etc.
Since ULPNode runs on very low voltage for a long time, and is able to be powered with USB, could it detect mains power outage, and be able to send a message, so I would know to go in and reset the gfi?