This is still a weird idea, but I sanded a hamster ball to make it diffuse an LED's light more evenly. This is an experiment to see if we can replace a Roomba with this simpler way of moving a sensor around a room. We can also gear it down to go slow enough that the sensor has time to get a good reading -- many gas sensors have 10-30 second latency so a Roomba is halfway across the room by the time the reading comes through.
The hamster ball is based in a toy called the "weasel ball" which is pictured in this video; if you remove the tail, it will "explore" a room in a similar manner to a Roomba. Mine is going to be larger and much slower, have a formaldehyde sensor inside, and light up in colors to represent the gradient of detected contaminant, for a GlowDoodle-style image.