Though, if you can budget to go through FCC Verification testing (class B), maybe around $1000-1500 depending on your test house, it can sometimes be quite a useful learning experience for a board of moderate complexity. It is surprising where RF leaks out of these days. For a device that is this simple, it is probably fine. Officially, my opinion is that you should always have all the proper certifications in place.
Unfortunately, the $10k U2F certification is not that unreasonable compared to other similar certifications I have seen... As the fees don't just cover interoperability testing, but also legal fees if the trademark or specification must be defended.
