Hoisin
This is Hoisin ([w]ho is in - groan), a simple Node.js application to let you know who's currently at work. It's great if you have remote workers, an office in another country or simply a big ol' office where you can't see everyone!
It works by continuously scanning the network and recognising the MAC addresses of people's computers. When a machine wakes up in the morning, it'll connect to the network and seamlessly mark that person as being present in Hoisin. When it goes to sleep at night, Hoisin detects that it's no longer on the network and marks that person as out of the office.
Installation
You'll need Node.js, Redis and nmap installed on your machine for this to work.
On OS X, you can get all three at once with brew install redis nodejs nmap.
From there, clone this repo and run coffee app.coffee. The app will pop up on
port 8080 and start scanning immediately. You can then send users to
http://<your_ip>:8080/enrol and start getting them to register their machines.
They'll then show up at http://<your_ip>:8080 for everyone can see.