I think the domain name would be very valuable to a radio station -- however, I think the problem with selling it is that Wireless is more of a computer term, and fm is more of a radio word (although, radio does involve wireless transmission)..
Anyhow, I think you'll find a buyer sooner than later -- especially once .FM becomes more widely known.
I bet that in a year from now, you could easily fetch 3 times this amount.
-Merlin