Before manufacturing a fully miniaturized system it is always wise to prototype at a larger scale first. This will help find bugs that will reduce the likelyhood of having to do a board respin later. In my case, must of the components I wanted to work with could easily be bought on Adafruit of Sparkfun with easily breadboardable headers.

In this breadboard prototype, I connected two Teensy LC micro-controllers to two wireless transceivers, microphones, speakers, etc. I wrote some code to configure one as a transmitter and one as a receiver to test the communications protocol/procedure, bitrates, and the system as a whole. Here are some of the lessons I learned:

1. The 3.3V regulator on the teensy is not powerful enough to power the receiver and speaker at the same time. I needed to have an external, higher-power regulator.
2. The Arduino library for the RF transceiver doesn't support the high-data-rate mode so it had to be modified for this application.
3. Any mic used needs high gain in order to be able to hear a human voice while attached to a lapel. Because a mic amplifier takes up valuable space and power I have found a mic that has an internal low-power amplifier. In addition, the teensy has an internal amplifier than can be used if additional gain is needed.
4. I thought the RF module had built features that made it simple to operate ( such as a power-on-reset feature) but it has been proven that it doesn't. Therefore, I have found that additional pins need to be connected to support all the modes I need.
5. Some times the Teensy doesn't play well with the RF library, therefore a manual reset button is a must and board space must be used.
6. The speaker amplifier consumes considerable power so it is necessary that I choose an amplifier that has a shutdown mode.