I bought a GNS5870 a few months ago to use an an external gps with ForeFlight on my iPad. I continually had trouble with it shutting off and on unexpectedly because of the lack of an actual switch on the unit. I finally gave up on it and bought a XGPS150 and used it while flying for the first time last weekend. It worked very well and ForeFlight had no trouble with it. The precision showed 10 meters which is certainly good enough for me. An advantage of using an external gps is that you are not dependent on the cellular system nor on the sim card in the iPad which can fail at unexpected times. Since I am using the upgraded georeferenced version of ForeFlight (shows my position on the approach plate) i particularly want that to always work when I need it. I am hoping to fly a challenging (for me) DME ARC at KMTN and I think that the iPad will help me do that. The image is of the XGPS150 app page from my iPad.   It works pretty well for knowing how it is working.