howmanypeoplearearound calculates the number of people in the vicinity using the approximate number of smartphones as a proxy (since ~70% of people have smartphones nowadays). A cellphone is determined to be in proximity to the computer based on sniffing WiFi probe requests. Possible uses of howmanypeoplearearound include: monitoring foot traffic in your house with Raspberry Pis, seeing if your roommates are home, etc.
Tested on Linux (Raspbian and Ubuntu) and Mac OS X.
This is cool way to check how many people are around you, but mind you it is not easy and you need to be technical to do few stuff. For more you can check out https://github.com/schollz/howmanypeoplearearound