GPS Tracking Device

I run an outdoor training program for high school student.  One of our exercises is teaching survival techniques in the wild.  I want to send them out in groups by them selves and see if they can survive for two days.  They have different objectives to complete during the time in the wilderness, which leads me to my question....

Because of liability issues, I can't actually leave them completely alone.  However, the goal is to make them think they are completely alone. To accomplish this, I want to secretly place a GPS tracking device in each groups belongings so that I can track their progress and mistakes along the way.  I need a device that can I can use to track each of these groups.  

I know of numerous devices that use GPS tacking technology that interface with Google Earth, but this will NOT work for me b/c I don't have access to the internet where I'm going.   Also, I have found a few technologies that use radio signals, but these won't work either b/c I will rarely have line-of-site with the groups - it is a mountainous region so getting a direct shot to each device will not be possible.

What I need is a few GPS tracking devices to place in their bags and then another GPS device with a mapped display that I can use to see all these devices in relation to where I currently am at.