I'm mostly interested in what goes wrong.

I've made enough of these projects to know that ~75% need modifications that were not anticipated. For instance, I made a freezer temp sensor to php email for cases where the freezer stops working... but when I opened the freezer, it would send an email. I needed to sample for 30 minutes or something.

Maybe this was simple and you will be part of the 25% that work perfect and need 0 updating.