https://iwringer.wordpress.com/2015/10/08/taxonomy-of-iot-usecases-seeing-iot-forest-from-the-trees/. Those devices can be used to solve a wide range of problems. Obviously, it is hard to do a complete taxonomy, yet writing even a subset down would help us lot with understanding IoT. The taxonomy is arranged around people, and each level moves further away from individual and becomes high level. Different levels are categorized from personal (e.g. wearables) to macro-level control ( smart cities). The following picture shows each category.

1. Wearables
Appliances
Smart spaces
Industrial
Internet
Service Industries
Smart Cities
Smart Home
SG Smart
Health