> Unfortunately, many of the smart locks that use your phone as an unlock mechanism don't have a good solution for what to do when your phone battery runs out.

The only z-wave smart locks I've seen carried in national retail stores also have keypads [1,2,3]. Isn't that the solution to the battery problem?

What lock do you use? I could never rely on z-wave to open mine; I only use that to automate locking up the house at night in case I forgot. It can take up to 30 seconds for my lock to respond to a z-wave command if it hasn't already been woken by some other event, which is a long time to stand outside your door waiting for it to open for you.

1: http://www.homedepot.com/p/Schlage-Camelot-Aged-Bronze-Touch...

2: http://www.homedepot.com/p/Schlage-Aged-Bronze-Home-Keypad-D...

3: http://www.lowes.com/pd_497751-350-910+TRL+ZW+15+SMT+CP_0__?...