I took an ESP8266, linked it to my laptop, then used Linux to tell me the wifi power in real time. By pinging the device at 500 Hz, I could get many data points to get an accurate signal reading.
This data can be used to light up an LED, for long-exposure pictures, or, to be recorded and composited into 2D or 3D data.
For this project, in the data set that is displayed on the project page, http://cnlohr.github.io/voxeltastic/
I used a 360x360x180mm area on my friend's oversized wood mill.
I'd love to see what people think about this project and if anyone does anything else like it!