As per #1, is WiFi really that bad? Because Geofencing is used quite extensively in the iOS ecosystem and doesn't seem to affect my battery that much at all... although I'm likely just missing what the feature was advertised as, possibly its something different.
Best WiFi today will consume about ~2mA when in standby. They are using ElectricImp which is a little worse.
People often look at "sleep" current of a WiFi module and think "oh boy I can run this for 2 years at like 100 micro amps". That is true if the WiFi module is turned off; useful if you are waking up, taking a reading, pushing data to the cloud, and then going back to sleep. But for a door you need to be listening on the network for an incoming packet all the time. How else would you know that the user wants you to open the door right now?
Alkaline AA batteries AT BEST have ~2600mAh of capacity. They run at 1.5V. You have 2600 x 1.5v = 3900 mWh of energy in each.
A Wifi module consuming ~3mA and 3.3V runs through that power at around 3900 / (3.3 * 3) = ~394 hours or about 16 days. 4 AA batteries and you'll get about 64 days or little over 2 months of usage.
Of course you'll get FAR LESS because:
A) You have to convert battery voltage to 3.3V and you'll get about 85% efficiency for a high current (300mA peak) needed for a WiFi device
B) You burn more energy when you actually send packets
C) You need quite a bit of power from those 4 AAs to actually turn the lock so you can't do the math assuming all your power is available for WiFi.
A number of Qalcomm Atheros chips like AR4100P. Gainspan's GS1011 and their newer GS2000. Pretty much anyone supporting PS-POLL should get around that range.
Electric Imp gets close to that but they are over it a bit I believe.
The challenge with door locks is that I'd like to change the battery every couple years, particularly on infrequently used doors. Most people can understand having to change batteries every couple months on a door they use frequently, but let's say you have a storage locker - it kind of sucks that every time you go to the locker, the battery is dead.
I wouldn't mind it if I had to mechanically charge the other side of the lock from the outside. Attach something to the door knob so I can "jiggle" it from the outside to wake up the unit and have it do its thing.
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.
