1No need to build
For testing purposes you actually do not need to build one of these as it's just a esp8266 any dev board will work for testing and developing the software for it
2When you need to build
for building this project get the schematics first. It's just a basic connections for ESP. The important thing is a 1N4148 diode which work as a 5v to 3.3v level shiftier well if you have a 3.3v serial connection then you can skip the diode.
And also R1 and R3 it works fine but then when you will program the chip you have to take special care not to use these pins (gpio 15). i did not tried to skip R2.
It is a simple circuit you don't have to follow what i have did.
But this is what i did
take a piece of perf board solder 7 headers to it then take some bare copper wire and make a ground pad on the solder side of perf board for coin cell where then you can solder a battery clip. Take some more copper wire and solder it to the esp8266's RESET, VCC, GROUND, TX pins (4 separate wires). then pass these 4 wires through the perf board and solder on the solder side and make the connections to the header. REMEMBER the coin cell is also coming in so keep some room for it.
do the remaining connections with some thin wire like wire wrapping wire etc
To program i'm using an Arduino UNO if you have USB to Serial converter use that. Here i'm telling how to do it with UNO.
1. First of all short the reset pin of Atmega328p to ground either using the female headers or the ISP header.
2. connect GND, GPIO0 to GROUND on Arduino
3.connect ESP TXD to TXD of Arduino
4.connect ESP RXD to RXD of Arduino (remember these are TXD & RXD not TX & RX where you connect TX to RX and RX to TX)
5.Connect VCC to 3.3v on Arduino
6.Now start Arduino IDE and compile the code after selecting the right board i usually go with generic modules
7.Now connect RESET line to GND and let it go and hit upload in IDE(if you're not getting it try couple more times)
8.after finishing your code should run and you'll be able to see some debug output in IDE serial terminal
9.If you're not able to program check the connections or try other board type
Now when everything works remove all wires between arduino to ESP add a COIN CELL and connect BATTERY PIN and VCC using a jumper block
you're ready to stick it "I DON'T KNOW WHERE"
(careful not to try it on anyone other than you)