Which phone is using KaiOS?

Can you elaborate on which phones are currently utilizing the KaiOS operating system? As an individual interested in staying up-to-date with the latest technological advancements, I'm particularly curious about the range of devices that have adopted this innovative platform. Is KaiOS predominantly found in feature phones aimed at providing basic functionality, or have there been any instances of smartphones integrating this operating system as well? Moreover, are there any notable manufacturers known for incorporating KaiOS into their product offerings? Lastly, could you perhaps provide a brief overview of the features and benefits that KaiOS brings to the table, particularly in comparison to more widely recognized mobile operating systems like Android and iOS?