Here is my project that uses Deep Sleep mode on an Adafruit HUZZAH ESP8266 and waken by a PIR motion sensor. It then reconnects to WiFi and sends an email via IFTTT.
Battery life went from about 3 days to over 6 weeks and still going strong.
Details available at https://github.com/rgrokett/ESP8266_PIRv2
![Image](https://cdn.instructables.com/FPC/1YK7/IQYT0793/FPC1YK7IQYT0793.MEDIUM.jpg)