If this is a kind of modernized and open PDA, (whoohoo, back to the Nokia N770 we are!) then it needs a discernable difference from a pinephone to be useful on its own. (Otherwise the potential LoRaWan backcover can cover your needs). For me, a killer distinction would be a 4-5" eink screen, which allows to show, incoming mails, messages, the time and your next calendar entries, while sleeping nearly all the time (it could wake up like every 1-2 minutes, fetching data updating he screen, and going back to sleep). The battery could last weeks!
A low-spec cam on the back to scan qr codes and business cards and a runtime of +1 week and I am in.
A low-spec cam on the back to scan qr codes and business cards and a runtime of +1 week and I am in.