I got the next messaging system up and going.
I am not sure on the BOM but I think each unit will come under $20
- Probably the most expensive part is the Wemos D1 mini at $5.00
- The 16×2 LCD with I2C connector would be $2.50
- The voltage regulator is $1.00
- Breadboard is $1.50
- Buzzer, LEDs, resistors and mosfets have to be less than $2
I think I am going to gear up to build 5 more.