Movement / habit reminder watch face

[Kartoffel]

Hi! First of all thanks to @joeycastillo for creating the Sensor Watch, it looks like the absolute perfect amount of smarts I'd want to wear on my wrist with an excellent development community behind it.

I'm planning to write a watch face to interrupt periods of hyperfocus or prolonged immobility, and remind myself to change posture or take a stretch break. I have a fairly well-defined plan, but I'd like to run it by the community and ask some firmware-specific questions before I start ordering sensors and writing the watch face.

Problem statement

Often when I'm deeply focused on a current task I end up sitting in the same (bad) posture for hours on end, ignoring all signals from my body to change it or to take a break. This happens often enough that I've developed back and neck problems, and they're not going away without training myself to take regular breaks and developing a more dynamic posture.
Developing new habits turns out to be one of the most difficult things for me, where everything I try either doesn't help or helps for a little while before I fall back into old patterns. I can really use an external reminder to pull me out of the focus and trigger me to take a mental step back and evaluate what my body needs.
I've used many timer/reminder apps on my phone, but I find they're too easy to dismiss or ignore, or I end up temporarily disabling them and forgetting about them completely. I used to wear a smart watch that could help out a little bit, but that ended up promoting a phone dependence and other nasty habits. Sensor Watch seems like the ideal in-between solution.

Proposed solution

I am developing a watch face for the Sensor Watch that sends periodic reminders. The reminders don't have any content, it will be up to you to decide what to do with them. Think of it as a quick alarm that goes off at a regular interval.

For those who would like to get reminders to get up and move, I plan to incorporate feedback from a motion sensor so that you will only get reminders after a period of sitting still. Many accelerometers have very low-power motion detection features, so the main Sensor Watch processor should not need to wake up from sleep much.

The main focus for me will be the functionality with an accelerometer sensor board, without it the watch face becomes a simplified version of the interval or tomato timer complications.

Options

The above ideas lead to the following customization settings for the watch face:

• Active hours: start and end time for when the functionality should be enabled, with an option to disable during weekends.
• Motion: send reminders based on inactivity (using accelerometer) or on a regular interval, should fall back to interval when no compatible accelerometer is detected.
• Reminder interval: remind after this many minutes of inactivity or using this regular interval.
• Sound / light: Sound buzzer, flash backlight, both, or none.
• Auto-dismiss: display reminder until the user dismisses it, or automatically dismiss it after a certain time.

I hope to include all the customizations necessary to make the watch face adjustable for your situation, so feel free to leave suggestions for features or customization options :)

Questions

This leaves me with a couple specific questions for now:

1. The watch face runs in the background, where the 'reminder' alarm functionality should be able to 'take over' the active watch face and display a reminder until it is dismissed. I think this should be doable using _wants_background_task or the background task scheduler, but I can't find much information on these other than existing faces. Is there any documentation on this?

2. What accelerometer to go for. I've noticed that there is a (supposedly tested) sensor board design around the LIS2DW accelerometer. It seems perfect in terms of features, only it's been marked as "not recommended for new designs" by the manufacturer. I can order them along with some flat-flex prints of the current design right now, but for the sake of future users it might be wise to switch to another accelerometer. @joeycastillo what do you think?