Thanks for sharing ideas.
Camera built in GPS main flaw is long GPS acquisition time, after camera is switched on plus (or minus) that most DSLR cameras don't have built in GPS at all.
But geo tagging can be done also afterwards in Lightroom and why not to all cameras, if there is GPS track log file. When entering to Amazon search "GPS data logger", there appear many dedicated commercial ones.
Common drawback of these is short battery time and need for a PC to download and check the track fitness, which may be not available on several day long trips. Most of these GPS loggers don’t support USB storage profile and track files can’t be transferred either to Android smart phones or tablets.
But with cameras I always have with me Canon S95 for quickies and I could change it to Canon S100, if it could record GPS log track.
The Canon S100 could be ideal hardware basis for GPS data logging and when track file is written to SD card it can be easily transferred each evening for checking to tablet or smartphone, when travelling light.
As the next concern is batteries of course, then there anyway are spare ones with me, if one doesn’t last until evening.
That’s the story and I hoped that someone already has come to it and the solution might be present already.
And I don’t have S100 to check it out myself and I haven't used CHDK yet.