Only yesterday I discovered I could play an adventure game in emacs. Then I discovered a bunch of layers and modes that were awesome. I haven't begun to scratch the surface, but if I buy a new Nexus 6P can I just flash Emacs on it?
Google "Termux emacs".
I started using it purely for the novelty of running emacs on my phone (a moto x pure) and it's a great piece of software. It's even open source!
Otherwise, the Logitech K380 Multi-Device Bluetooth Keyboard ( https://www.amazon.com/dp/B0148NPH9I/ref=cm_sw_r_other_apa_l... ) is great.