iPad mini with GPS synced to inReach mini GPS

Typically in iOS, the paired iR device presents itself through location services. A client application, such as Gaia, which uses location services has no direct control over which of the available GPS receivers it uses. The client application specifies the desired accuracy and location services does its best to return data with that accuracy.

That might involve choosing among available GPS devices, augmenting GPS-derived data (from whatever source) with things like WiFi and cell tower info, etc.

Gaia won't know the difference.

You won't be able t tell much of anything unless you take a bunch of readings with and without the Mini and do statistical analysis on the resulting dataset. Frankly, I doubt that the Mini is going to do any better than the onboard GPS hardware.

Adding to twolpert’s response - I use a Garmin Glo2 with my iPhone for mapping work (stand alone Bluetooth GPS) with my iPhone. . As he noted, IOS determines which GPS source to use and the application just gets it from the location services.  The only way I can tell which is the source is the the app I use logs the gps and the Garmin glo2 will provide up to 4hz while the standard built in gps is only 1hz (like most watches).  If I block the Glo I will see an eventual switch back to 1hz from the phone GPS. Android is very different with more flexibility (and the Glo can provide up to 10hz apparently).  The most likely advantage to using the mini as a source is you can place it in an optimum position and not worry about where your iPad is.  No idea however if you could actually figure out where the location data was coming from anyway.  With the glo, besides the higher data rate, I find it is far better at limiting the GPS meandering you get when you stop which makes setting waypoints much more accurate..  in general I find the tracks seem more accurate but this is really hard to truly validate. 

two & raw: Thank you both for the responses. This is very useful information.