I own the EF-610 DG Super and operate it off-camera using wireless optical P-TTL and wireless optical simple slave as well as wired P-TTL and manual flash using Pentax 5P cord and shoe adapters. A third-party 5-pole shoe-and-cable adapter may be substituted for the Pentax version at considerable savings (
Example at B&H), though not with the built-in flash as part of the setup.
Here is a photo of my K-3 using P-TTL with built-in flash balanced against the Sigma EF-610 DG Super using the Hot Shoe Adapter FG, Cord F5P, and Off-camera Adapter F.
...to take the example photo below...
Addendum:
Here are the components I have except for the Hot Shoe Adapter F in the photo above.
Also available, though sometimes hard to find, are 5-foot and 9.5-foot 5P cords.
Steve
P.S. I found all of my bits and pieces for about 1/2 of regular retail pricing, but it took some effort.