Now there are cellular phones that might do this. But that would take an engineer the first time.
I think old school spotting scopes are a much better idea. Most ranges will have one or the range master has one.https://www.google.com/#q=target+spotting+scope
I have an odd question. Ism a target shooter, going up 800 plus yards.
At the distance, evaluating your shots on target is difficult.
Could I use something like a wireless security camera set out with the target, nearby Lind distance router, and see the target 800 yards away on my iPhone.
Thanks for advice?

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