I was an early user of "unnamed" popular Kickstarter door lock and I took my dog out at 9pm and came back to find that the batteries were dead.

I called the customer support and they told me the low battery alert message was sent after I had locked the door and left, which was about a 20 minute trip.

They ended up paying for my locksmith, but I haven't felt comfortable using the lock since so it just sits on my door.