elveax:
Also, last question for anyone still reading: if I'm using a 3.7v LiPO to power my ESP8266 and my HC-SR04P, I'll at least need a linear voltage regulator to drop it down to a safe voltage, right? Something akin to this?
elveax:
Correct - NodeMCU. Eventually, I'll be wanting to put the ESP8266 on a PCB by itself, however, so I imagine I'll need to have whichever step-up device I use in-line between the power supply and the sensor? And then a voltage regulator between the power supply and the VIN on the module?
The NodeMCU already has a 5V regulator. I don't know what type.
The regulator you linked to sounds suitable at first glance, except that it is surface mount. Unless you are skilled with working with surface mount components, and have suitable equipment, it may be better to find something on a breakout board.