I live in a mountain area and need to cover around 3 miles. Highest ground elevation would be around 10,000 feet and normal operating 9300' or a little lower. Required hook up to a smart phone is not possible. Smaller the better. Any suggestions.
3 linear miles around a perimeter, or 3 square miles?
Would you be using it with FPV, or having it fly a pre-planned route with waypoints?
That's a decent amount of area to cover, plus higher elevation/thinner air/less lift = less duration, range, battery life. For that situation, and with that requirement, I'd start looking into building my own. Look into FPV drone racers - the tech is easy, plenty of info out there. I'd avoid anything by DJI, Hubsan, or the major chicom companies. Always questionable on what/how they're connecting to. Plus their software updates can really mess things up. .
Though there is one possibility that might be worthwhile looking into - getting a used DJI Phantom 3 or 4 and jailbreaking it with Litchi, and then not doing any updates. The reason I mention used is they should already have been connected, and set up to run. Buying a new one means registration with the company, and the companies servers, to activate the UAV. Still going to have to use an old smartphone - only as a display screen, but removing the sim card so there's no cell capability. Run it in airplane mode, controller connecting to drone. Personally...I wouldn't trust it. Especially if you're trying to be noticeable in this current world.
If you need something smaller - something say that fits into an alice pack exterior pocket, look at some of the mavic clones that are out there. Stuff that's on ebay. Still will need an old smartphone for a display though....
Yet another thing you'll probably have to deal with is antenna design - if you're really going out three miles, a yagi would be a good idea. Just another thing to consider.
Plus I'm not going to get into the legalities like Line of Sight requirements, Airspace restrictions, etc, you can figure those out.
I think the answer for you is building or buying an FPV racing drone and customize it for your needs.
Another thought, might not work for you but something to think about, would be making an aerostat and building a mount to take an 8k surveillance camera.......pan/swivel/zoom and you have lots of capability. Easy to see though, unlike a drone. Once you get those high enough...you're not seeing them from the ground.