Codec2 is an open source speech codec used by the ham radio mode FreeDV. The main draw to Codec2 is the very low bitrate required to sustain quality speech, which is very useful on HF so that bandwidth can be kept small, and signals can be received with low SNR.
I stumbled across a cheap module using the Si4463 chip, which is able to transmit and receive (G)FSK, 4(G)FSK, and OOK with a wide tuning range in the VHF and UHF bands. I've been looking for a use for these modules for a while, and while doing some research on Codec2, I believe I have found an application. Using a low-cost ARM microcontroller, I plan to implement a data transceiver that is capable of communicating using Codec2, to be used by hams (partially because these modules do not appear to have any sort of FCC certification). In addition to voice, I would also like to send low-rate data across the link as well.
With my senior design project starting to increase in workload, I won't have much time to devote to this project, but I plan to make slow, steady progress on it when I can.