I've seen people from day to day are asking for tethering support for the current or just the later Pentax DSLRs including the K-5, K-r, 645D and K-7 etc., which all lacks such a function. Recent examples:-
http://forums.dpreview.com/forums/readflat.asp?forum=1036&thread=36797719
http://www.pentaxforums.com/forums/pentax-dslr-discussion/120241-tether-my-k-7-k-5-645d-please.html
And yes, back to the old *ist D till the K10D/100D days, there was the software of Pentax Remote Assistant. But then this feature and support was dropped later on. As for competitors' products, say, every Canon EOS DSLR can be controlled via the bundled EOS Utility software, with software updates that are uploaded to Canon's websites for downloading from time to time, too.
But, I just don't understand how important this feature really is, on the other hand. If you just need just a "tethering" feature, get a Web-Cam! ;-D My opinion is for most of the time, cameras are used outside for shooting, not connecting to a PC indoor! Right? :-)
So, as you can see, last time when I think about the shortcomings of the K-5, the lack of tethering option is just Not one of the big ten reasons for still why not the K-5, as I don't think it is just significant enough to be a real issue. Nevertheless, I think the 645D, as a studio camera, would be better to have such a feature, so that images can be downloaded to the computer directly immediately after shooting. But then the 645D supports Eye-Fi, doesn't it?