Just a thought here,

When you depend on two devices to accomplish a single task, ie a phone to interface with an inreach device, you have twice the chance of failure. More stuff, more chance to fail. . .

I totally understand that the idea of two devices and certainly a decent GPS is expensive, but, what alternative is there?

I can't say I have been greatly impressed with Garmin's GPS. They used to have a few competitors in the handheld GPS market, but today not so much. I know Lowrance dropped out of the handheld market several years back, and I've not seen anyone use a Magellan handheld in some time. Fewer manufacturers means less competition and my feeling is that Garman has slipped in the innovation department in the last 20 years.