Here is another smart gadget that lets you see who is at your door from your smartphone. The Crukee WiFi HD Video Doorbell is powered by a 3000 mAh battery that lasts up to 90 days. It is smart enough to stay asleep until activity is detected or someone rings the bell.
This video doorbell has a 1.3MP HD camera and 2-way audio. It is weatherproof too. Costs under $130 at this time.