Nitinol and Nitinol Engines

I remember working with this stuff back in high school. Seemed like magic at the time. Amazing alloy. But if I remember correctly, it is quite expensive.

While I'm not a big fan of the title of this video, "Free Energy Nitinol Heat Machines invented in the early 1970"
...I hope they're talking about Gibbs free energy..., the video is quite interesting.