For an easier alternative to using these example, the [ESP8266HTTPClient library](https://github.com/esp8266/Arduino/tree/master/libraries/ESP8266HTTPClient) can be used (which also supports HTTPS via a SHA1 fingerprint).
this article makes BLE (bluetooth low energy) seem pretty attractive compared to ZigBee; BLE is said to have lower power requirements (it lists current draw for RF4CE but not for ZigBee, but it says that RF4CE is similar to ZigBee; RF4CE current draw is said to be too high for a CR2032 battery), better range, and better resistance to jamming; and BLE is said to be able to do mesh networking with the addition of an application)
J. Yoon, B. Noble, M. Liu, and M. Kim. International Conference on Mobile Systems, Applications and Services, page 177--190. New York, NY, USA, ACM, (2006)
H. Liu, Y. Gan, J. Yang, S. Sidhom, Y. Wang, Y. Chen, and F. Ye. Proceedings of the 18th Annual International Conference on Mobile Computing and Networking, page 305--316. New York, NY, USA, ACM, (2012)
J. Krumm, and E. Horvitz. Mobile and Ubiquitous Systems: Networking and Services, 2004. MOBIQUITOUS 2004. The First Annual International Conference on, page 4-13. (August 2004)
H. Shin, and H. Cha. Proceedings of the 2010 IEEE 16th International Conference on Embedded and Real-Time Computing Systems and Applications, page 105--113. Washington, DC, USA, IEEE Computer Society, (2010)