I wish I had something useful to say, but that sounds honestly amazing. If you could do wifi at the same time, then that'd be a perfect email/ssh/irc device.
i think that the esp32 is probably a decent microcontroller to use for this purpose, in place of the pi zero; it does have a decent sleep mode and also wifi
its energy efficiency per instruction is not the best but is certainly acceptable
its energy efficiency per instruction is not the best but is certainly acceptable