Lockitron is highly hackable, based on the video. A guy made bananas create tones based on pushing on them, and that set of tones opened the lock. You'd buy lockitron at that point as a way to interface with your lock in a more reliable way than whatever you could throw together.

Secondly, what do you need cell service for when communicating with a device via bluetooth? Or NFC? Or WiFi? No one's being excluded here except the unimaginative.