Found these on ebay. About half the cost of others I have found. To use them with 240v you would wire them in line controlling the coil of the relay. When the GFCI trips it cuts power to the coil and to the panel or heater element depending on which relay it is wired to. $20 shipped. I bought one for the panel I am doing right now. I like that the GFCI will be integrated into the panel itself.
http://cgi.ebay.com/ws/eBayISAPI.dl...70623&ssPageName=STRK:MEWAX:IT#ht_5744wt_1139
http://cgi.ebay.com/ws/eBayISAPI.dl...70623&ssPageName=STRK:MEWAX:IT#ht_5744wt_1139