Wireless shutter button for the OM-D E-M5?

Is there such a thing as a wireless shutter button for my camera, or is the wired version my only option?

The wired option is not a deal breaker, but Olympus' wired shutter button is considerably more expensive than most wireless solutions, even their own (though they don't say it's compatible with the OM-D), and I find that a bit odd.

Can anyone here shed some light on this subject?