I make an integrated scale system for derby racing . System is 4 hot-wired bathroom scales that talk to a central brain. These are helpful in getting the weight balance and cross-bind tweaked on a soap box derby car to match the track. As the cars are all identical, getting the perfect weight balance is one of the few tweaks one can make to gain an edge.
Initially built for my own use. There is a trickle of demand (2 to 3 systems a year) for the systems on ebay. I used up my stock of off the shelf cases and built my own for the next round of orders. Used thick PG Acrylic for a bullet proof result.