I built my own controller - it uses an ADAFruit 9DOF module, an XBee and a Teensy. The idea is that holding it in your hand parallel to the ground is neutral, tilt up for acceleration and tilt down for braking. It works pretty well, but there are some gotchas.
Originally I wanted to control the board with my phone, and I had a working version, but the more I worked with it the worse an idea it became, for 3 reasons - 1) I can’t shoot vid when I’m boarding, 2) if I crash I might break the phone and 3) I now have several boards, so letting friends use the other boards would be a challenge.
The upside of the controller is that it is very intuitive, requires no buttons (except an enable/disable button) or levers to drive it.
The downside is if things go wrong people tend to throw their hands up and that just makes it worse, and sometimes people forget to disable the board when we aren’t riding and they flip the thing up and the board runs away. I will fix this with a deadman sensor on the board but I haven’t gotten around to it yet.
The next rev will have a nice 3D printed case and some additional controls (like cruise control).
The other mistake I made was putting the power button right next to the enable button. This confuses people for a while. Next time I’ll have a buried power switch - probably a slider or rocker.