Permission required error with new Timer() in Backgroundservice

Timers can't be used in the SeviceDelegate.

Well, that's unfortunate.

How do you handle retransmissions then?
When communicating the onError is called when there was an error sending the data. You usually retry this a couple of times but wait a couple of ms between each retry.
How am I supposed to wait before the resend without a timer?

If you get an error, one cause would be if the watch and phone aren't connected. The way I handle that in a background event is if phoneConnected is false, I don't even make the request, and just return an error status. The background has at most 30 seconds when it runs, so I don't even bother retrying, and just check again the next time the temporal event runs.

For other types of errors, can't you just retry without a delay? It's kind of a kludge, but if you want to wait a bit, you can enable sensors and then use the callback to get awakened every second or so. I experimented with this in a test app, but not production, as the app will then also need senor permissions, but not actually do anything with the sensors.

Have you considered doing what you're trying in a widget or a watch app, where you can just do everything in the main app, use timers, etc?

I could try without a delay, but that is not very hardware friendly usually. The sensor trick seems very 'hacky', I'm not sure I'll try it, but nice find nonetheless :)

I haven't. I'm writing a watchface where I display the time, and lots of other info from the phone too. Could be a watchapp, I don't know the drawbacks of making it a watchapp instead of a face. It should be the main watchface whenever the user comesback from anything (widget/app/activity, whatever).

Displaying the info in a widget would make it easier to implement, and it can be only a screen away from the watchface. As a watch face, I'm guessing you'll run into problems where users will want other things that are common on WFs - steps/calories/intense mins/floors/sunrise/sunset, and many more, so you may want to consider that part too.

Yeah, those are on the watchface too :) Though not all of them, but configurable. I'm pretty sure I'll need a real device to see what's better for this, but I know if those restrictions on communications and timer didn't exist it would definitely be a watchface.