yeah... keyboardists are pretty much resigned to a permanent spot somewhere at the back of the stage with the drummer. or else, just simply ask for your keyboards to be right at the front of the stage all the time so u'll forever be in front, wireless or not.
nonetheless, if you must, i'd say m-audio midair is a good fuss-free option with the built-in transmitter.
Let me poison you with this clip..
http://www.youtube.com/watch?v=Bz4h-LcAoHU