Several boards are discussing this. If you're interested, among the most complete sets of possible answers are those on:
http://www.qi.com/talk/viewtopic.php?t=17494&postdays=0&postorder=asc&start=510
and
http://network.laxpower.com/laxforum/viewtopic.php?f=15&t=38303&p=671588#p671588