spydeer
Spydeer is a tool that logs the mac addresses connected to your wi-fi. You can then assign devices and names to the addresses and see who was connected when.
How to use
Make sure you have arp-scan installed (this is what is used, with administrator privilege, to fetch the mac addresses.
You need to install ruby, too. Then, run gem install sinatra sequel rufus-scheduler thin and launch the server with rackup !!