push button switch for powering Arduino or ESP8266

I am using a CR2450 battery:

http://data.energizer.com/PDFs/cr2450.pdf

OK then read the datasheet. Note the parameters under "Pulse Drain" - they cite 9.0 mA.

This is apparently the maximum intended. Does that sound different to the 500 mA pulse for the ESP8266?

Recommended batteries for ESP8266: minimum two "AAA" cells, alkaline.

Or the LiPo from a mobile phone.

Not arguing the data but other people have done it and worked:

https://medium.com/@kstevica/how-to-build-an-open-wifi-finder-using-esp8266-and-two-coin-batteries-9c31eb6f9859#.z39v1su3b

brolly759: Not arguing the data but other people have done it and worked:

Perhaps because receiving beacon frames for listing available Access Points is a receive-only process?