One of the challenges in automating existing lighting in the smart home is when there are more than two switches currently connected to a lighting fixture, you want to make it "smart" and you also want the switches to work as they always have. The solution in an existing home is very much dependent on how these existing switches have been wired.
The intermediate switch is a versatile switch and can be used for most lighting situations, but it is more expensive, so you would normally only use it when needed. When you have three switches controlling one light, the middle one needs to be an intermediate switch and the others need to be two way. Should you want 4 or more switches then it is possible to add more intermediate switches between the end two-way switches.
We have developed a solution for installation in new house builds that resolves the issue with multiple light switches and also supports smart bulbs.