I noticed your profile and would like to offer you my project. We can discuss any details over chat. I am currently creating a prototype that I think you would be an expert for. Using the Adafruit arduino hardware, I have created a passive GPS tracker, I am looking to progress this project and add in an active component that can alert when a physical boundary has been broken (RF?). Both of these concepts have already been done with other bits of hardware, however my idea incorporates another component that makes it unique. So to summarise, I am looking to create a high frequency passive GPS tracker that incorporates an active component that can alert the user when a boundary has been broken i.e. Trackr or loc8tor. Let me know if this is something you could do and would be interested in and we can talk more specifics.