I have a K-01 and the Cowboy Studio NPT-04 set works perfectly with it, and with my Yong-Nuo 460-II and 560-II flashes (the "-II" is important).
Reliable range is 30 feet. If you want a lot longer than that, it's Pocket Wizard time, for a good deal more money. But the Cowboy receiver/transmitter will get you outdoors in daylight -- where regular infrared optical flash washes out in the sunlight. The Cowboy also triggers through walls... you can be outside and set off a flash that is inside. I wrote a full description of all this on the Xara-Users graphics forum, at
http://board.xara-users.info/viewtopic.php?f=29&t=5003 ... since then, have used the NPT-04 set on my K-01, no problems.
Now. if you are thinking of making a buck with radio wireless, check out Scott Hargis' website -- at
- Lighting For Real Estate Photography ... his videos are worth every penny of their cost. Sweet spot is applying what you learn not o jobs for cheap real estate agents, but for industrial and facility photography for small-to-medium size corporations that make things. Good luck!