A look at the ESP8266 for IoT

Another nice feature of the ESP8266 and ESP32 chips is that they run from 2.3V up to 3.6V. This means that you can easily power the chip, without needing any voltage regulation besides perhaps a capacitor, from 2 AA(A) batteries or a 3V lithium battery like a CR2. Since it has some very lower power modes, this can be enough to keep the chip running for a year while polling a sensor every so often.

If power it not a constraint, then especially the ESP32 is a very powerful chip. See for example the Odroid Go device for an example of what you can make with it: https://www.hardkernel.com/shop/odroid-go/