Difference is you're charging your iPhone every day. WiFi is power hungry, but the iPhone 5 has ~1,500 mAh of power, and WiFi takes a continuous ~50 mAh. That gives you around 30 hours of constant wifi usage on an iPhone. Now that's not counting everything else happening on the iPhone, which is quite a lot, but this is back of the envelope math and I'm hoping I can reveal the order of magnitude involved.
On the Lockitron, it depends how long it takes to wake up and ping while maintaining a low latency. In this case it's probably something along the lines of: wake up for 25ms every 1s and check if somebody's unlocking. This saves you 95% of power usage (950ms/1s aren't spent powering wifi) with a max of 1s latency. But I'm not sure if 25ms is enough to ask for new messages over wifi. This still gives you 2.5 mA averaged, which will drain that iPhone battery in 600 hours, which is only 25 days.
And I bet this sports a smaller battery than 1,500 mAh.
On the Lockitron, it depends how long it takes to wake up and ping while maintaining a low latency. In this case it's probably something along the lines of: wake up for 25ms every 1s and check if somebody's unlocking. This saves you 95% of power usage (950ms/1s aren't spent powering wifi) with a max of 1s latency. But I'm not sure if 25ms is enough to ask for new messages over wifi. This still gives you 2.5 mA averaged, which will drain that iPhone battery in 600 hours, which is only 25 days.
And I bet this sports a smaller battery than 1,500 mAh.