I was discussing the concept of having a chair sensor with @tgauchat just a few days back. The problem is that we don’t have an easy way to do this using a sensor dedicated to detect occupancy of a chair. While accelerator based approach may be a plausible approach, I dont think it will help me know the current occupancy state of a chair.
The use cases I was thinking of are on the same lines of what people have been suggesting in the thread. But it can also be potentially expanded to small businesses like local pubs, restaurants etc where the state of a bar stool or chair can be made available on their website or just help them run some useful analytics - Which will help their customers plan better and help the businesses meet their customer needs better.
I was thinking of a cheaper and effective way of doing this but it may call for new hardware development. Ideally, it should be something that is easy to place on any kind of chair (wood, sofa, recliner, wheel chair etc) and secondly it should be cheap - May be something less than $25 per sensor, so that people can afford it for all their chairs and Thirdly, it should be transparent to the user.