Initial work on OPORCON 2 (my version of OPORCON) is finished. Inital data can be found here.
Next, I found out that iButton idea is ancient, at least since 1999 (remember, SportIdent dates back to 1997, Emit in 1995). Too bad it "died", maybe EMIT and SI equipment would be cheaper today.
And last, there is an product in Ukraine, similar to OPORCON, called iButtonSport. The only difference is that it's not a real time system because runners carry the microcontroller boxes, while iButton chips are the controls. In that system they need to collect all of chips to check what was happening in the woods :D The funniest part is that by small change in their PC software they can get OPORCON functionality, with current hardware.
As I wished, OPORCON is improving. David Deane (in amateur radio world better known with his callsign G3ZOI) took OPORCON and made some of the improvements mentioned in the text. With help from Bjorn Dinse PA4BWD, he upgraded Oporcon with: better timing although still using internal clock, audio signal, control ID change in the box using a DIP switch. He also made a clean schematic and a PCB, and improved download software!
This system is used regularly on ARDF competitions in Great Britain, without any problems. David was so pleased he made an article for RSGB's (Radio Society of Great Britain) magazine RadCom.
Please check David's page , Bjorn's page (on Dutch, but Google translate can cope with it), David's article (I don't host it and I don't know what's the extent of copyright of it's article) , and Orienteering wiki pages with links on videos of some of the mentioned mods.