There are two primary uses that I will be putting the BadElf 2200 to. Unlike my phone, this device can happily chug along all day turning out a highly accurate GPS track all day and night on a single charge. Not only does this allow us to see where we have been but it helps with the the geo location of photos (more that later).
The 2200 is equipped with Bluetooth which mans that it only can you transfer the created track files back to your phone or iPad it can actually supplement the inbuilt GPS (or supply full GPS in the case of a wifi only iPad) both on and off wifi connection.
This is incredibly helpful. As I discovered while hiking through the hills of Myanmar last year - your iPhone's GPS is deactivated when the phone is set to flight mode. I found no way of turning the GPS only on without taking the phone out of flight mode and draining the battery as it constantly searches for a signal.
Another use I am keen to put the 2200 to is to assist. With geo tagging our hundreds (and thousands) of photos we take while travelling.
With some software wizardry, I can time match the time of the photo taken with an exact location. Regardless of which camera or device I used to take the photo. One of the hardest things to do after coming back from Myanmar was the reconciliation of 6000 photos with which temple or holy site the photo matched. Using freely available software I can import the track file and have the photos located by the time they were shot.
NB - all of your devices should be set to the same Timezone otherwise you will need to do some time correcting.
If you have a lot of travel across multiple countries, I would suggest using GMT or Zulu time and adding the appropriate corrections in segments. There are any number of applications, some web based, who will take the tracking file (usually gpx) and geo code your photos. Simple search geo code photos using gpx track.
I have been using the 2200 on longer road trips and found. That after 6 hours of constant tracking less than 5% battery and 10% memory used. This includes over 20000 individual tracking point