I would recommend looking into a GPS data logger. In their most basic form, it's basically nothing more than a GPS receiver that logs to an internal file. It doesn't require any connection to the camera so you can use it with ANY camera. Since it's camera independent you don't need to worry about wasting money on a Canon adapter if you switch to Nikon down the line or if you want to take just your P&S along instead of a full dSLR rig. It also doesn't tap off of your camera battery, so that's one less thing to worry about. And no cords or adapters hanging off of the camera either.
B&H stocks a number of them, these 3 are some of the highest rated on their site;
Sony GPS Image Tracker - $90
It runs ~15 hours straight off of a single AA (one reviewer said 30+ on a lithium AA). ~5-10 minute sat acquisition time off of a cold start. This is one of the few, if not only independent loggers that I've come across that will tag your photos on the spot. It has a SD slot built into, pop your card out of the camera, pop it in and it tags your photos. That function seems to have it's limitations though. If you're shooting RAW, you're out of luck unless you shoot a Sony. Additionally, it will only tag a batch of 60 images at a time; so if you shot 600 images, you have to repeat the procedure 10 times to get them all tagged. Mediocre software, not directly MAC compatible out of the box*. Comes with a little vinyl carrying case with a clip. Supposedly will even charge over USB if you use a rechargeable AA in it.
Holux M241 - $64
~12 hours on a single AA. Similar acquisition times as the Sony. No SD slot, but it does have BT. This would allow you to get the BT adapter for your specific dSLR and it would auto-tag all of your EXIF data. Not directly MAC compatible*. It allows you to change the plotting point frequency based off of distance traveled or time elapsed. The biggest issue I've noted about this model is that, if the battery dies before you've saved your track, you just lost your entire track for the day. It apparently just cache's the track log instead of actually writing it to the memory. One reviewer said its a simple fix, just get it out and save the log every now and then, but IMO that's just one more thing to remember.
GiSTEQ DPL900 - $60 - $10 instant rebate = $50
The cheapest of them all. Built in LiIon battery good for ~10-17 hours. Appears to have the quickest cold-start time of them all (though for the most part, this really isn't important). Terrible software* I'm not a big fan of this one other than based on price. If you forget to charge it overnight, you're pretty well screwed, you don't even have the option of picking up a (highly overpriced) AA from the gift shop. Granted, I keep a 2000mah external USB battery pack in my bag, but that's to help keep my phone charged throughout the day.
I've asterisked the software on all of these for a reason. While all of these come with some flavor of software, some of it terrible, it's important to note that you may very well not need their software at all. All of these units write a basic text log of GPS cords and a time stamp. Aperture, Lightroom, PhotoMechanic, etc are all capable of importing the GPX log (some need freeware plugins). There are quite a few good standalone freeware programs on Windows, MAC and *nix platforms that will merge the GPX log into the EXIF data as well.
I know there are both Android and iPhone apps that accomplish the same thing for FAR less money (usually $2-4, some even free), but they rapidly consume the battery and, from some reading, don't seem to work all that well, all of the time. I can barely keep my EVO on for 8 hours with limited use, let alone with something constantly grabbing at the GPS.
Overall I think the Sony is the nicest of them all. If you're not shooting RAW, being able to transfer to your EXIF data, completely standalone with no PC at all seems pretty nice, but then again one additional step in my post workflow really isn't a big deal. It has the best battery life, doesn't appear to suffer from lost log files if the battery does die, can charge from USB, etc etc. Of course, it's the most expensive of the three, but it's still half of the cost (or less) than most of the camera-specific wired or wireless modules out there, plus it's completely camera independent.
For those that don't understand quite how these external devices work, they simply log GPS cords and time stamps. The software then compares the time stamp on the picture's EXIF file to the time stamp on the GPS log. If the EXIF timestamp was 13:11:23, it looks for that timestamp in the log, grabs the associated coordinates and copies them into the appropriate EXIF data fields. All you need to do before hand is turn the logger on and toss it into the top of your camera bag / backpack / whatever you are carrying for the day.
HTH!
But it may be another toy I have to get when it comes out for Canon.
