What are the real subminiature cameras ? I don´t have expertise enough to give you an answer. Someone could claim that 110 format cameras are a desecration when considered as a subminiature cameras. The truth is that when the 110 format in the early Seventies was introduced, the production of the former submini cameras, and the film they used, ceased, also processing became more expensive and harder to find.
Some really good subminiature cameras exists, Minox in the frontline. Almost every respectable camera manufacturer had a line of 110 format cameras. Even 110 format SLR cameras were made (Pentax, Minolta).
This page consists a kind of peek to the world of the miniature cameras. You can find wonderful internet sites which are "specialized" to subminiature cameras. Take a look at these pages by D. Scott Young,
As far as the 16mm movie film is available you can reload the film cassette quite easily and to have it processed in lab that can process and print 110 film. Not very convenient or easy but possible. Still I dare to write that the use of subminiature cameras is over but in case that You are a bit "old fashioned" and eager to to be busy you can get a wonderful and cheap hobby among these little cameras. Cellular phones could be considered as the next generation of submini cameras.