Recurring notification when door is left open for XX minutes?

Hi again, I seem to be confused as to the hub they are all over with different prices & strength. Can I get this hub on Amazon or where?
Then I should get the Left it open Device?
Many thanks for your help.
Sincerely,
Susan Kay

Also how do I know if I need to make sure it’s large evough?
Susan

Make sure you purchase the “Now it’s closed” device as well so you have both open and close covered.

But which hub do I need? Samsung or?
How do I enlarge the font on here?

I’m beginning to think I will have to buy most all that is sold. Where I just wanted a System that tells me if the gararge is left open.
Sincerely,
Susan Kay

This and this should allow you to do that with Smartthings. I use the Iris branded versions but the Go control is the same thing I believe.

You could also go with something simpler and cheaper like this.

So I installed the piston and modified it accordingly (here is original)…but I don’t receive any notifications. What did I do wrong?

Thanks