GPS waypoints that can be set in the field

I’ve been thinking about the creation of dynamic waypoints. I would like for the user of my project to be able to walk to a point in a field, press a button on the custom controller, and have their current location added as a waypoint. From searching online I cannot find a MAVProxy command that simply replays the current GPS position of the UAV. It must be possible for the system to make a request for the current GPS location, as this is used when setting the home location as the position in which the UAV was switched on. It is possible that this is handled by some lower level MAVLink commands, without their being an interface to do so manually using MAVProxy. If I cannot discover a method of gaining the current GPS location, I could potentially have a GPS module within the controller, and get the co-ordinates from that. Waypoints are stored in a text file. MAVProxy can load this file to the UAV, and so I would need to be editing this text file with the desired waypoints. This will be stored on the Raspberry Pi, and so having a GPS module connected to the Arduino (which is in turn connected to the RasPi) could be a viable method of getting co-ordinates to write to this file.