Muisejt:
You are certainly correct. However, if you cell phone battery dies, or you are in a "dead signal" region, as I frequently am, this could be problematic. Still, thank you for your response.
Seriously, don't discount the smartphone option.
I researched heavily into getting a GPS and ultimately landed on... wait for it... my iPhone.
Syncing the GPX track is dead simple and your iPhone (or whatever smartphone you have) does not require a cell signal or wifi to track your location. I've also found that the free app "Trails" in the app store is also very simple to use and does an excellent job.
Camera mounted GPS receivers are all plagued in one way or another. They either are horribly expensive (Nikon), or take forever to lock a GPS signal (all of them), or drain camera batteries (all of them) or don't work indoors (all of them) or have some other limitation.
Using your phone doesn't require you to add bulk to your camera or pack, is a better GPS tracker than most GPS trackers (since it'll also use wifi and cell towers if GPS can't be locked), works decently indoors and it's something you have with you always, anyways.
You could get a handheld GPS unit and use that, sure. But that's another device that you have to track, turn on/off, keep charged or bring spare batteries for, it also doesn't have cell or wifi as backup if you're indoors or heavily wooded area or..., etc.
I used my phone on my last 9 hour photo outing and started w/ battery at 83% and ended with battery at 71%. The new backgrounding of apps on iOS makes for very gentle use of the battery on your phone while keeping very good track of where you are. I also ended up with a GPS file with over 500 GPS points, more than enough to accurately track my location (usually when taking a photo you're stopped for long enough that there will be a track for that exact spot). Sync the GPX file to the images using any number of ways and done.
Your cost to try the smartphone option is zero if you use "Trails" or similar. There's also free syncing software or Aperture (and Lightroom, I think) will do it.