Have you looked at the features offered by apps and devices currently available? GPS for the blind is an extremely crowded field.
For IOS alone:
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$1*
$1* Sendero LookAround
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$1And then there are Android apps, as well as custom built GPS devices for blind folks. I don't know what accessible GPS solutions exist for the Apple Watch, because I don't own one. If there's nothing, that might be somewhere to start? But something tells me Blindsquare introduced Apple Watch support a few versions ago.