Got an ATP Photo Finder, a device that supposes to tag all photos with GPS grids. 
First test:
Turn it on, it get the GPS location quick.  Leave it on my car's dash board to make sure it is under full sky all the time.  VIsited friends took pictures.  A few hours gone by, look at it and notice it TURN OFF.  Yeah, look like it run out of battery.  THat is very fast consider I have a full charge of eneloop battery in it.  Thus, I cannot tag any pictures I took on that day.
Second test, make sure GPS location detects, make sure the time on my camera and GPS is very close (neary match each other).  Drive on freeway to an office.  Took multiple pictures.  After finish taking pictures, I turn it off.  Of course, I don't want it to run out of battery while I spend time workiing in my office.  Try to tag the 41 pictures I took.  I make sure the time zone selection was right.  The result is all UNSUCCESSFUL.  Even if it cannot tag because it (might) lose data when I turn it off.  It should save the GPS data in an NVRAM, not just a RAM that lose all data when it does not have electricity on it. 
Not only I found that it does not work for me.  It is very annoying when the LCD is automatically off too soon.  In less than 5 seconds, the LCD will turn off.  YOu have to keep pressing a button to turn it on, so you can see the time (to setup time on your camera).  Even when it is trying to tag your photos, it turn the LCD off and you have no idea what it is doing.
In sum, do not buy it.  At least not at time time.