The Geocaching app on the iPhone with VoiceOver affords a way to search for the presence of geo caches in your area, but as far as using it in an accessible way, it is a bit of a challenge as the app has a compass to direct the user but the compass position is not relayed over the VoiceOver. What you can get from the app is the latitude and longitude of the cache itself which can then be entered into another app that is more accessible. The app BlindSquare (costs about $29.99) allows a user to enter their own landmark via latitude and longitude by editing the coordinates. The technical part is that Geocaching displays coordinates in a hybrid form (e.g. 32˚ 49.818′ N and 116˚ 46.574′ W) while BlindSquare uses Decimal degrees (e.g. 32.8303˚ N and 116.7762˚ W); luckily there are free conversion apps you can get to do the math for you. Some of the students on Team 6 might enjoy this challenge while the students in much more functional programs on Team 3 would likely benefit from you preparing the app for them and saving the landmark for your outing.
BlindSquare can provide directions with cardinal directions (N, S, E, W), relative directions (To Your Right, To Your Left, etc.), or clock face (toward One O’Clock, or Three O’Clock), and can have distances express as feet or meters.
The app will get you close to the cache but locating the actual box will be more manual. One way to adapt this is to arrive early and to have a small sound emitter placed at the cache or coordinate directions with tactile landmarks that will be clues to bring the students in closer. At some point you may be able use things like iBeacons and Nearables (just visit Estimote for fun dreaming about how you could use the technology).
There are many off the shelf products for those with a lot of usable vision, such as the Garmin Colorado series with big bright screens, but to allow a combination of visual and non-visual students to really have access to the same information, the VoiceOver and app combination is about the only thing I am aware of.
Hope this helps!!!