Leash sensor? / doggie bag reminder

I’m looking for suggestions on how to remind our family’s dog walkers to refill the doggie bags that are attached to the dog’s leash. I’m new to Home Assistant.

We’re looking for the most reliable and easiest solution, and generally trying to avoid batteries, having to have our phones with us, nor remember to take some action when we get home. We have an Alexa Show and Google Hub near the door and where the leash is stored.

A few ideas I had:

A hook sensor with an automation where it prompts on a nearby speaker when the leash is returned to remind the person to refill the doggie bags. I can’t find any hardware that would work as a hanger (I’m thinking something like a 3M hook).

The same hook sensor with a simple speaker announcement when it goes off hook to check the bags.

A Bluetooth beacon of some kind attached to the leash where a nearby speaker reminders the person when they open the back door (returning with the dog).

A beacon of some kind on the dog’s collar. She’s a 15lb dog so it would have to be small. When she comes back in range and the door is opened send a reminder to a nearby speaker.

My first idea, albeit a lot more complex, was to track how many bags are left. A roll of doggie bags has 20 bags, each time the leash is returned, the person answers how many bags were used, and that number is subtracted. The user can confirm and update the number of bags left as it approaches zero, and when it’s refilled. This might be too complex and prone to failure. I also wasn’t sure if it’s possible to have any kind of responses back from notifications to speakers (e.g., ask a question and logic based on the response).

I’m interested to hear your ideas!

Thank you.

ESP-Home.
A reed sensor.
A strong magnet on the leash to hang the leash on the wall / somewhere close to the reed sensor.

Or if you want off the shelf.
Replace ESP-Home and reed sensor with a door sensor.