Correct me if I am wrong are you talking about the stair chair lift for the elderly by any chance?
Rose, as a CAP contractor I have installed several of these over the past few years. What would you like to know about them? Typically insurance has paid for this with a prescription from DR. There are some really nice ones as well as some pretty junky ones that are hard to use and break down a lot.
If you have an open stair well you can also consider putting in an elevator. We have done a few of these as well. One house we cut out a window on each floor and installed the elevator on the outside. Re-sided that area put two doors where the windows were and when they were closed it looked like a closet door. Many builders in our area are putting closets in main hallways these days and framing just for that reason in the future.
I had one installed for my husband when he became disabled. It was a life saver! After he passed away, I kept it; it was invaluable to me when I had my hip replaced. Now my elderly guests occasionally use it, and it's great for transporting laundry up from the basement. I think EVERY house should come with one!