This chapter describes research in and development of more user-friendly rest rooms which are equipped with intelligent modules based on the Ambient Intelligence (AmI) paradigm. This enables the novel rest room prototypes to partly adapt automatically to the individual needs of the person who is currently using them. The three main target groups were older people with functional limitations, people with disabilities and carers. The iterative design process applied was strongly user centred and actively involved vulnerable people in the area of intimate needs. Thus, particular care was given to consider the taboo effect and the protection of vulnerable users. Five iteratively improved rest room prototypes were designed and evaluated in a laboratory environment. A reduced prototype was also tested successfully in a day activity centre over a period of 2 months with 29 primary and 12 secondary users. It was found that the intelligent toilet prototypes were useful and able to increase the autonomy and independence of people with functional limitations. From the point of view of an engineer, the continuous involvement of users was considered to be extremely essential and necessary in this area of intimate needs. Although there was no direct involvement of people with dementia, several comments and findings of relevance for them were collected, for example, the reduction of cognitive load during use of the intelligent rest room. A basic version of the new toilet system was put on the market in 2006.