Finally, someone did it! :-o Here it is, we should thank Tomasz, especially for all those K-5 and K-r users!
http://www.pktether.com/new-version-0-6-0
It is said that now Debug mode of *any* Pentax DSLR can be activated, including K-5, as this is re-confirmed by Tomasz in his reply in the comments section of his post, i.e., K-5 is fully tested.
So, go get the software and try it yourself. Enjoy! :-)
P.S. The Mac version of the software has not been successfully built yet, as told.
P.S. 2 As for other older Pentax DSLR models, the Debug mode menu can be opened in-camera: Method Here and Full Tutorial Here.
Update (1-9): Go onto the Next Part:-
Successfully Open the Debug Mode of My K-r! :-)