I looked into this in a posting on priuschat.com (post #23 on this thread):
http://priuschat.com/forums/prius-hybrid-news/47058-hidden-hybrid-automobile-dangers-what-you-should-know-about-emfs-3.html
I found two listings of EMF readings for cars, and the Prius was no different from any other car. The listings are here:
http://www.eiwellspring.org/EMFMeasurementsOfCarsAndTrucks.htm
and post #4 in this thread:
http://forums.mikeholt.com/showthread.php?t=99889
The upshot is that the Prius is no different from any other car. You can get much higher EMF exposure from many household appliances and electronics than you do from your car. Even if you are worried about EMFs, your car (including your hybrid) should be low on your list of worries.