To play devil's advocate, it is less conspicuous to open a door that you can hack open with your phone than it is to pick or bump it (Although depending on your skill, picking it may be a very easy thing too).

Lockitron will send you a message when the door is unlocked, even if it's using a bump key.

I wonder what the minimum viable wifi-jammer is here?

Have you considered any sort of pingdom style monitoring for that sort of thing?

(Obviously, it's a really unlikely scenario right now, but if they can keep it off the air long enough to open the door and introduce it to Mr Big Hammer, notifications may not be forthcoming :) )

The minimum viable radio jammer is a high voltage spark. Not very subtle or safe though.

http://en.wikipedia.org/wiki/Spark-gap_transmitter

Building a proper one is still pretty easy. It's carting around a big enough battery that's the problem.