We're likely approaching the day when it'll be more cheap to attempt to build an open Linux phone from scratch rather than keep waiting for a manufacturer to listen to a few thousand techies who don't want their personal data chewed by proprietary OSes. That milestone will almost certainly be marked by the availability of cheap 3/4G modems (I'd be perfectly fine with 3G if it was the only option). We're not there but…
I just used new generation of the same display, and a one handed Twiddler 3 keyboard.
Raspberry pi doesn't have cellular, so I am looking at Zero phone project which has a solution. But so far I am already extracting value from my wearable computer in many easily implementable use cases.