The tool you are referring to is called a "carpet extractor" or "carpet cleaner." It is a machine that combines the functions of spraying water or cleaning solution onto the surface (such as carpets, sofas, and beds) and then immediately vacuuming up the dirty water, along with any stains, dirt, or debris.
Carpet extractors are commonly used for deep cleaning carpets, upholstery, and other fabric surfaces. They are effective at removing stains, odors, and allergens from various soft surfaces. In your case, a carpet extractor could be helpful for cleaning and deodorizing your bed if your nephew happens to have an accident.
When using a carpet extractor, it's essential to follow the manufacturer's instructions and use appropriate cleaning solutions that are safe for the surface you are cleaning. Also, make sure to thoroughly dry the cleaned area to prevent any moisture-related issues.