So some further thoughts. this project is mostly stuck on an efficient/cheap triangulation methods. My rotary encoders are not working :-(. I thought I fried the transistors by hooking it up wrong. But after replacing them it still doesn't work.

More on infrastructure thoughts would be to use the same ramps board but use kilipper with a rasberry pi to control the steppers. Next put all the logic on the PI. 

For triangulation I could use two usb mice mounted to the shaper. Then two tape measures mounted with the ends connected to the corners. Next run the tape in front of the mouse to get accurate x/y triangulation.

https://www.raspberrypi.org/forums/viewtopic.php?t=80987

Another thought would be to use two echo locators to triangulate the shapers position:

http://www.instructables.com/id/Dual-Sensor-Echo-Locator/