Just wanted to add that the Yongnuo RF-603 transcievers are EXCELLENT. I own six. They are not only transmitter and receiver in one (completely interchangeable), but they are also RF remote shutter releases. I used it that way last fall to do self-engagement-portraits with my fiance when my friend was suddenly unavailable the day we had arranged to do it. One remote in my hand, one on the camera with a cable to the remote port, and another on a remote flash for fill light on an overcast day. The pictures looked so great that nobody believed they were self-portraits until I showed them an outtake with the remote visible.
Just make sure you get the ones that are labeled for Canon because that comes with the right cable for the Pentax remote.
Oh, also, these things do ttl-passthrough for on-camera flash. Doesn't do ttl for the remote units, though. I've never tried it with a Pentax flash, but they list the Canon units as being compatible with Pentax, and the pins seem to line up. You can use Nikon or Canon units if all you want is a remote flash and don't need the remote shutter as well, and won't be using on-camera ttl flash. I tested both kinds (I bought mine before I switched back to Pentax; I had a Nikon and a Canon G10, and I used a Canon 30D at the studio where I was working) and they both fire just fine with Pentax.
At weddings I set up my G10 as a remotely located camera (overhead view of the dance floor, for instance), and it triggers the remote flashes just like the one on my handheld cameras. It's a beautiful system!!