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No tutorial really, I mainly installed Raspbian, the PI camera web interface, and gdrive (see links above). I do have specific steps I wrote down that I'll throw in a sharable doc if you'd like.
Power is just a USB car charger to an inline switch into the pi. You definitely would want to use one of these if you're going to do a permanent install: https://mausberry-circuits.myshopify.com/collections/car-power-supply-switches/products/3a-car-supply-switch-1
With my setup I have to remember to shutdown the pi safely over ssh before clicking the button (or run the risk of corrupting the SD). TBH it's not bad since I have the pi connect to my phone's hot spot, and have a button mapped to shutdown in this app: https://play.google.com/store/apps/details?id=uk.co.knowles_online.raspberrysshlite
You can use a Smart Phone and an SSH app to act as a keyboard. Connecting to the Pi via Bluetooth.
[Edit] Heck doing a quick search and found there is even an ~~Official~~ Raspberry Pi SSH Android app: https://play.google.com/store/apps/details?id=uk.co.knowles_online.raspberrysshlite
Could you use something like this?
https://play.google.com/store/apps/details?id=uk.co.knowles_online.raspberrysshlite
You bind buttons to commands that are executed via SSH. I wonder if a similar app is available for iOS.