The ESP8266 is the receiver that must read the signal and specify the direction depending on the RSSI. first problem is that the ESP8266 is not directional and the access points around are not directional either . second problem is that the RSSI information takes long time to be read by the ESP8266 . each 3 seconds I can take on measurement. small measurement number make it difficult to analyze the results . I don't know if it is possible to build small directional antenna for the ESP8266E or not . and is the accuracy of the device would be reliable and maintain the device size small or accurate readings ?.