With my experience, developing android apps in Java, 10-15 years ago, such project would need at least 2 developers, for 5-6 months of development and testing.
Then monitoring itself is not that easy as well. You need to distinguish between a planned vacation trip, and visit to a friend. And a lot, a lot more things.
To be honest, yes, it took me more time than expected. And now, with my current knowledge, next time, I will do it much, much faster, with less token. But this is how it is with every development. A junior developer will waste more time and money that an experienced one. With AI, most of us are like junior developers.
Most of the time, I waste, not with the app itself. But to keep it running 24/7, without in any way asking the parents to do any manual work. And this is because I did not know that Android based OSes are so aggressively killing long-running applications. I took my note :)
But to write it for a weekend, I just cannot agree. For a weekend, you can't make real and deep testing. A simple example: you need to run it for a few weeks, without opening it to see if Android will kill it, because it treats it as 'never used' app.