Alarms on Doors that have Access to a Pool
Not the answer you are looking for, but:
Loud Alarms are What You Really NEED
Assuming that the premise is a sound one, that people need to be warned of unexpected/unauthorized entrance to the pool area, a loud alarm is the right answer, not an electronic notification. A few examples:

It is all too easy to ignore texts/notifications/etc. &quot;If my boss/spouse/buddy texts me one more time about that project/trip/party, I'm gonna scream&quot; followed by ignoring the next 30 minutes of little beeps by just swiping them away to look at &quot;later&quot;. Kid wanders out...disaster.

A new cleaning crew comes in the day before your big pool party. One of them asks, &quot;can I bring my 3 year old, I'll keep an eye on her, she's a really quiet kid&quot; and you say &quot;sure&quot;. You go out to pick up munchies. The cleaning person starts vacuuming in the living room. The kid wanders through the door (left closed but unlocked because the crew is cleaning &quot;everywhere&quot;)...disaster.

You are out at the pool having fun. You hear a honk and go out front to greet the guests. He has the radio on in his car and you decide to listen to the last 2 minutes of the big game, radio blaring, watches/phones ignored (my day off, I'm ignoring texts), kid who was watching TV inside wanders out to the pool to find you...disaster.


You can argue whether any alarm is needed. But once an alarm is needed, an App won't substitute. Not when accident to disaster = 3 minutes or less in the water.
A number of people have pointed out that for a child even 3 minutes can easily cause major damage or even be fatal. I am not suggesting &quot;up to 3 minutes and everything is going to be just fine&quot; - quite the opposite, I am using that as a very short time period to indicate just how little time it takes - and therefore why an alarm on entering the pool area, hopefully a minute before falling in the pool is vitally important.
For those suggesting &quot;put up the stupid alarms and then unplug/remove battery/etc. after the inspector leaves&quot;, please don't do that!.