Netalyzer; WiFi Security (Android only)
 

Netalyzer is an Android appl (Google Play Store) that does a reasonably rigorous scan of a WiFi network connection and reports config anomalies. Some of anomalies are useful for determining if a network should be trusted.

Example:

Last week @ FNT, the DNS service was misdirecting 38 high profile domains to faux sites ... a good first step for a MITM attack. Which domains? microsoft.com, update.microsoft.com, apple.com, wamu.com, chase.com, wellsfargo.com, fidelity.com, twitter.com, etc.