Max,
I do not think if there is any kind of certification about IEC62304 compliance.
Let me put it this way, eventhough there would be a certificate, for what purpose would it be useful for you? Well ... it could give a kind of confidence that at the time of the issuance your operation may complies with it.
But ... i think we are in a great trouble if a third party should tell us whether or not we apply good engineering practices. We should be confident about it anyway!
And also, engineers should inherently apply best engineering practices, not because of a standard but because that is the way how to continuously provide reliable software. Simple is that!
One more thing.
I think regardless this standard keep saying any development method is okay, it still stipulates the waterfall kind of development. I really do not think that any competitive company can afford to accommodate this legacy kind of methodology. But it is not surprising. This standard has a long history back till the 7o's.
Recently, there is a AAMI TIR45:2015 "Guidance on the use of AGILE practices in the development of medical device software" guidance published, that tells you how to apply it to AGILE practices.
But hang on a second ... isn't it insane? Writing up a guidance for a legacy standard to justify how to read the standard when you want to do what 99% of the industry is doing?! And paying for both of these?! Outrageous!
So for me in this standard there are several good engineering practices defined, but unless coming out from the university and looking for some real thing, I see little or no value of it, because professional engineers applying these practices anyway.
Process sequence-wise I think it is utterly obsolete and misleading, only in some really large organization people having no direct contact with the developers may think that work is carried out accordingly.
Cheers!