Bell is offering its new "NumberShare" program to customers wanting to link their new Apple Watch Series 3 Cellular with their iPhone. And, based on what I've seen so far, the $5/month fee is the cheapest option available. At $5/month, the Series 3 with Cellular seems more and more worth the premium.
Of course, it's not available in Manitoba or Saskatchewan.
Fortunately, it looks like Telus supports VoLTE in Manitoba, so we should have some sort of service by year-end. No such luck for Saskatchatoon though.