One of the hardest things in Arduino-based designs is power savings, and this one is not an exception. This design has no power saving, which means it will onl

One of the hardest things in Arduino-based designs is power savings, and this one is not an exception. This design has no power saving, which means it will only last few hours tops on the batteries. This could be improved, but the current design (ESP8266 + analog IR sensor) does not really work with low power. A good start would be to put a 2nd low-power micro on IR encoder that'd (1) count pulses (2) wake up ESP8266. This will allow one to keep complex stuff (audio out) using Arduino libraries, while small piece of hand-written code will take care low power stuff. A more advanced design would be to get rid of ESP8266 and switch to low power MCU. If you keep audio uncompressed, a small MCU (STM8 or AVR8) is perfectly capable of playing some speech... and it will only take microamps in sleep/sense mode. You likely won't be able to use as many pre-made libraries however, so this is substantially more development time.