Take a look on Schneider Electric Harmony XB5R wireless and batteryless pushbuttons.
•25m with the receiver installed in a metal electrical cabinet
•Boosted to 40m with use of external relay antenna with the receiver installed in a metal electrical cabinet
•100m in free space.
Have used them and they works fine.
http://www.schneider-electric.ca/si...ocal/automation_and_control/harmony_xb5r.xml#
This looks like more what i would like to use.
There is a repeater option with a 5m cable have you used it? Can you just extend it further ? Can you have two repeaters, so i can put one on either side ?