NodeMCU may not be battery efficient enough as local sensor
Even when only waking up every 20 mins, it would still only last about 2 months with that battery capacity:
Each hour, the device would be awake 12 times for 6 seconds at a time, (72 seconds or 0.02 hours) and asleep for the remainder of the time (0.998 hours). So average current consumption in any given hour is (100*0.02) + (0.05*0.998) = 2.05mA So the 890mAh battery would last about 434 hours, or 18 days. That's not great, but better than my original estimates.