I stared with looking around on the web for either a case or a mount that I can use as a base to start and I deiced to go with a window mount type that I found on Amazon which includes a goose neck and suction cup that attaches to the phone bracket. Another item I ordered with it is a bar mount with a 1/4-20 thread screw which is the industry standard screw size for attaching any camera (just like on a tripod). The bar mount I plan to use for attaching directly to the barrel for future use.
As for how I plan to attach the bracket to the bar mount and other 1/4-20 mounts is pretty simple, I headed out to my local homedepot and hunted around for parts and this is what I came out with;
One of the holes in the corner bracket will need to be drilled out to 1/4" wide to fit the 1/4-20 bolt, simply clamp the bracket into a vise (failing that, screw it down into a piece of scrap wood) and drill through one of the holes with a 1/4" drill bit and if you have a way to deburr, you should to avoid a cutting hazard. The T plate will be affixed to two of the holes of the iPhone bracket with two of the 5.8x10mm nuts and bolts with the third set to attach the corner bracket to the T plate. The 1/4-20 bolt will pass through the enlarged hole which will be affixed with the 1/4-20 x 7/8" coupling nut where there will be enough space left in the coupling nut to thread onto tripod and other 1/4-20 camera mounts. See pics below for reference, it's a really straight forward build and should be done in under ten minutes.