When I had originally chosen the Huzzah ESP8266 breakout board, I hadn't used one before, and had envisioned using it as a serial-to-wireless transceiver to take the serial data from a separate microcontroller and pass data back and forth between the transmitter and the base station. But after having a look at its spec sheet, it's clear this little board has a lot more to offer. It's clear that I need to rethink my choice of components.

In addition to the wireless connectivity, it has nine GPIO pins and an analog input. That's easily enough for a Hitachi LCD on the base station or some push buttons on the transmitter, audio input, and a PWM output I can use as a DAC to generate audio output. So - it looks like I might not need that Teensy after all!

For the transmitter, I'd basically just need to create what is in effect an audio shield for the Huzzah, and some circuitry to turn power off and on. (It has no reason to be on all the time, so it will only power up when you activate it and turn off when the call hangs up.) For the base station, nine GPIOs probably won't be enough - it will make sense to have a separate microcontroller to handle some of the functions, communicating with the Huzzah over serial.

A Huzzah audio shield may be a worthwhile spin-off project, in and of itself. This wouldn't need the same power-on and power-off functions, as it would be more of a general purpose device.