am-i-working 
Logs your working activity based on /etc/resolv.conf domain.
The idea is pretty simple: when I'm connected in the company network or
VPN, a line with domain mycompany.com appears in my /etc/resolv.conf.
What I want here is to log those changes so I can easily get my extra working
hours later (and automate the sending of the report too).
To run it, you can simply ./am-i-working -d mycompany > work.log, or
create a service in the OS level to keep it running forever.
OSX Service
Create a file like this:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>Label</key>
<string>am-i-working</string>
<key>ProgramArguments</key>
<array>
<string>/path/to/am-i-working</string>
<string>--domain</string>
<string>mycompany</string>
</array>
<key>RunAtLoad</key>
<true/>
<key>StandardOutPath</key>
<string>/path/to/am-i-working-out.log</string>
<key>StandardErrorPath</key>
<string>/path/to/am-i-working-err.log</string>
</dict>
</plist>
Changing the path to the am-i-working binary, domain argument and where to
save the logs (usually /Users/USER/Library/Logs/).
Save the file in ~/Library/LaunchAgents/am-i-working.plist.
Then run:
launchctl load ~/Library/LaunchAgents/am-i-working.plist
And you can check that the am-i-working process will be running on background.