There are hundreds of circumstances that could cause you to cancel your trip, return home early or force you to seek emergency medical treatment while traveling.
There are many different companies. Here are a few recommendations but please browse around as services and prices vary.
Travelex The “Cancel for Any Reason” upgrade must be purchased within 30 days of the initial deposit/payment of your Covered Trip.
Travel Guard http://www.travelguard.com/ or Travel Insurance Services http://www.travelinsure.com.
American Express also has a good insurance plan for their premiere members.
TEN (Travelers Emergency Network) also offers a yearly membership for Emergency Evacuation Coverage
Medjet Assist 1-800-527-7478