The Aubrey/Maturin series by Patrick O’Brian

Longitude by dava sobel

Does it need to be an iPhone app? Is simply getting an alert via SMS good enough? If so, you could rig something with a raspberry pi.

$0.02

Personally, I had nothing but trouble with the Yale Smart Lock. The lock itself works. But integrating it with Wi-Fi and Bluetooth was terrible. $0.02

If you are interested in getting into programming, specifically python, there are devices like the esp32 and the raspberry pi Pico w. They are fun program and offer a lot of latitude for interesting projects.