I'm in the market for something like this for on call purposes. Something small/light enough to stow in a coat pocket but which has a physical keyboard and enough functionality for me to be able to triage most issues without having to resort to a laptop.
I've been trying the Gemini which almost fits the bill but doesn't quite cut it - the keyboard is OK but not backlit (I didn't think about how often that comes in handy when purchasing). I'll probably try the follow up 'Cosmo' when that comes out.
In another reply thread I mentioned that I'm using a $50 smartphone kit consisting of a smartphone stand(Nulaxy brand, but there are dozens of similar designs) and iClever folding Bluetooth keyboard for writing. I think this is roughly along the lines of what you might want. The keyboard fits snugly in a vest pocket(it comes in two versions - I'm using the larger version with full-size keys and backlight) and gives a decent - not amazing, but good enough that I don't care - typing experience. There are many folding Bluetooth keyboards on Amazon, but this one stood out from the pack.
Combined with the stand to raise my phone I have something a bit more ergonomic than most integrated-device experiences, definitely better than what I would get from a Gemini when a flat surface is available, and I can literally throw on my vest and go for a jog and then take out the kit at a coffeeshop and lose myself in writing without difficulty. You might also need more I/O or a full PC architecture, but this setup was like a "my search is over" moment for me.
I've been trying the Gemini which almost fits the bill but doesn't quite cut it - the keyboard is OK but not backlit (I didn't think about how often that comes in handy when purchasing). I'll probably try the follow up 'Cosmo' when that comes out.
Would love to see any other suggestions.