Just came across this controller board. It looks interesting and has a lot of good features.
100% GRBL version 0.9i (& GRBL version 0.8c) compatible
Capable of powering from ATX PSU
Capable of powering from a dedicated 12V/24V two wire power supply
Drive 4 motors with DRV8825 Stepper Drivers - 2.5A (peak) with 1.75A (RMS) with up to 1/32 microstepping
1 Driver capable of cloning X,Y, or Z or being run as an independent axis
Hardware support for both USB and Wireless Operation (XBee, WiFly, or blueBee)*
Emergency Stop to cut all motor power (with optional override)
12V and 5V** outputs for powering peripherals (fans, pumps, vacuums)
Quickly connect to Stepper Motors and limit switches with 3.5mm screw terminals and/or 4-pin 0.1" (2.54mm) headers
Expansion port for coming upgrades (handheld jog controller, integrated spindle speed control, etc.)
Just might have to pick one up to see how it works.