Irongeek put together a simple program for monitoring network shenanigans when you’re on an untrusted network like the coffee shop. It sits in the Windows Systray and notifies you about a variety of events. It alerts you when it sees the MAC address of the IP gateway change. It watches the security log and warns you of any attempted or successful logins. The firewall log is also monitered. Try it out and send him any bug reports/feature requests you might have.