The Dropbear is the latest Speeduino ECU and is a fully assembled 8+8 channel board powered by a 120Mhz Teensy 3.5.
speeduino.com
John, the developer is currently working on implementing a knock sensor that feeds back to the ECU as well.
The more basic (but still very capable) version of speeduino runs $160 for a fully assembled board. 1/10th the cost of a Haltech 750 with equal/greater capabilities in pretty much every way. Obviously, details are left to the user to sort out like weather proofing the ECU, interfacing with crank/cam sensors (adding a cam sensor for R3s) etc.
Just a neat development that's way overdue in arriving since the Megasquirt project basically turned into a cesspool of disfunctional ECUs.