If you've been waiting the EZ-Robot 4-in-1 sensors, they are available 2 for 1 at Brookstone. https://www.brookstone.com/ez-robot-4-in-1-orientation-sensor/950594p.html
It's a bit of a problem getting the deal if you are outside the US so phone them to place an order and they will make it work.
Great find !
The 4-in-1 sensors and other parts are even cheaper now. $9.95 for 2 sensors!
Just ordered 2 of these sensors, have no idea what I will do with them but.....