Use the onboard WiFi chip to scan accessible Wifi networks locally.
Sort them, and select the two strongest ones, based on the Received Signal Strength Intensity.
Use the onboard Sigfox module to send these two Mac adresses to our application server.
Sigfox allows for a 12-byte useful payload, so we can send two 6-bytes mac adresses over the network.
Another way would be to send 2 messages (= 24 bytes) so we can combine MAC Address + RSSI for higher precision
Upload the following files to your SiPy :
main.pysigfox.pywifiscan.py