I got the G5 the day it became available in Australia. I’d seen announcements that Dexcom had released an Apple Watch app, so I thought I would easily get that up and running. Long-story-short: the Apple Watch app is available for those living in countries that use mg/Dl scale only, while much of the planet uses mmol.
I thought WatchSugar might be the answer, but the app is solely in mg/Dl (although creator, Adam Wolf, said Dexcom uses different authentication servers for non-US users and couldn’t access to them to develop support for them. As his code is Open Source he said he hoped another developer might pick it up and run with a mmol option).
Dexcom has said they intend to offer this, but as I’m tired of waiting I thought I’d reach out and see if anyone has any other ideas to crack getting mmols and trend info on the watch. has anyone else taken a crack at this?
I had the same issue, there is no workaround, sorry. I have accepted to live with re-calculating the values, knowing that 70 is lower limit and 130 higher… Time enough you will stop recalculating. 
My dedicated monitor (which I use at night) is locked on mmols. Also when sugars drop, confusion is a factor and I don’t want to add another scale to the mix. I wish Dexcom would simply get an FDA approval on the app in mmols (how hard can that be) so a workable solution for non-US users was available!
They have the mmol app, so no need for FDA or the European agency approval there, but the link to apple watch and Clarity is missing. Why? Lazy developers and product managers I would say. The only thing they need to do is to take the US app and change the algorithm and voila. But no. I don’t know how many emails I’ve sent to Dexcom asking for this development…
I’m using the mmol app which works on iPhone, but it doesn’t include an Apple Watch sidekick. Glad to know there are others out there pushing for this. Otherwise my Apple Watch isn’t very useful (I bought mine on the strength of Dexcom’s early positive noises and prototypes for AW).