Whenever you use WiFi away from your home or office network, you're potentially open to attack. There are plenty of dangers out there, including scam networks masquerading as real public hot spots, and "evil twins," which are rogue duplicate networks set up at a public hot spot, and appear to be the real network, when in fact, they're run by someone who wants you to connect so that he can break into your PC and steal your personal information.
This freebie promises to help. It monitors the networks to which you connect, and if they're potentially dangerous, issues warnings and offers advice on how to keep yourself safe. It also warns you if you connect to an unencrypted wireless network, or if you've connected to a wireless network that can use encryption, but you haven't enabled it.
There's plenty more it warns against as well, such as potential phishing attacks, and even sudden changes in signal strength.