Correct, a few VoIP providers offer semi-solution to 911.

http://www.vonage.com/features_911.php
http://www.usa.att.com/callvantage/faqs/about_911.jsp

Definately not a good solution for people that travel with their VoIP box. But a decent solution for the household. If your VoIP provider does not offer 911 service you have two other options:

1. Some landline telephone lines will still provider "911 only" service when the line is disconnected.
2. A cell phone. Any cell phone will work(even deactivated ones), as long as the phone is getting a signal.