I know what you mean, and have seen it advertised, but have no actual experience of it.
If you think about it though, how could it really work?
In Canada, we don't really have primary medical insurance, we have provincial healthcare, paid for out of our taxes. Most of us also have subsidiary medical insurance to pay for those items, dental etc, that are not covered by the province. Most of these however are subsidized by our employers as a employment or pension benefit.
Remove this subsidy and the premiums would double or even higher, and you would end up with a situation like US healthcare insurance where you have an extra 'layer' between the patient and healthcare provider, who has to make a profit.
Insurance is to allow us to financially survive a disaster that may not happen. That's why it can work for some things but not for others.