If your smartphone ships with a stock Android ROM you'll notice that new versions have added the feature of letting FM radio work without headphones plugged in.

If your smartphone ships with a stock Android ROM you'll notice that new versions have added the feature of letting FM radio work without headphones plugged in. Also if you really don't want to have wires around you can buy a jack tap antenna (not sure about the naming, making it up sorry) or.. just plug in the headphones and cut the wires away from the jack (and as a precautionary measure insulate it).