While working with Biodata Sonification I have found that connecting multiple plants to produce music can be challenging.  One key aspect of this biodata system is Isolation of the plant sensor, like a medical sensor we need to ensure that the plant is not impacted by the sensor in order to detect how it reacts to stimulus 'in nature'.  One way this is done is by using MIDI which is opto-isolated, an additional level can be provided by bluetooth and wifi wireless connections.  

Bluetooth MIDI is very well implemented on most Android and iPhones, as well as modern computers, making it a great way to connect one (or perhaps) two biodata systems to a computer/phone.  

In order for plants from multiple locations to be monitored/listened to simultaneously, we can use RTP-MIDI.  This service allows MIDI to be sent over a local or external network.  By using services like McLaren Labs MIDI Cloud we can connect multiple MIDI streams from around the world!

After a series of iterations, I have a successful BOM and design for the circuit board.  I needed to abandon the ProMicro inclusion on the board (for space and sanity).  This design of the boards will work with any Adafruit Feather main board, specifically built for the ESP32 Feather, Huzzah (ESP8266), or 32u4 Feather.  I'm hopeful it would work with some of the Bluetooth boards, just need to ensure the pins in usage for the IO and MIDI are not conflicting.

All of the files should eventually make it to my GitHub repository, and I have attached the 'current' version of files to this project.

I also have designed a neat (simple) 3D printed enclosure which allows a LiPo battery to be stacked along with the Feather and Biodata boards.  Check it out on Tinkercad.