I used these resources with my students when I found some old Ti-83 calculators laying around in the science storage closet. NASA has an entire educator guide built with 10 lessons to use with your students. NASA Calculator Robots
So in addition to the ti-83 calculators (it also works with some other models too) you need to purchase the robot base. A company called Norland Research sells the this based on your calculator model for around $99. Norland Research
For us this was an inexpensive way to get students programing "robots"