VPNs are great for allowing you to do certain things that require being on your company's network while you're on an external internet connection. At Viget, we use a VPN for a number of activities: connecting to internal servers, viewing secure internal websites, deploying the latest code to certain servers, etc.
Recently, while working from home, I kept noticing that my internet felt slow. I'd hop on over to speedtest.net and see much lower than expected results. Before calling up my ISP, I noticed that I had forgotten to disconnect from the VPN! Connected for 8-15 hours, routing all of my traffic through our company's private network! :(
So, I came up with a solution: a small ruby script that runs every 10 minutes to check whether I'm connected to the VPN, and if I have been for more than 10 minutes, yell at me.