I2C EEPROM (on I2C0 - same bus as the accelerometer)
A ‘battery low’ LED
External circuitry (D-latch) to turn on and off the whole unit, drawing only 1uA when off.
The ability to turn on the unit by booping the bottom half of the Wio Terminal. The unit can turn itself off by bringing a GPIO high.
I also did a battery test today. With almost all the peripherals on, the screen and accelerometer running, but without WiFi running, I get a little over 3 hours with an 850mAh cell (4.2V → 3.2V)