Let's retrofit a device over my door that will sound an alarm and send an alert if it is left unlocked or closed, similar to how a refrigerator door works. I got this idea after seeing products that are almost the same as this that can be used on doors and windows. I customized my own version that fits onto my own door and detects both the locking state and the position of the door from the lip using a hall sensor and magnets. If it is unlocked or opened for more than 5 minutes it will sound an alarm, it will also send a notification to me alerting me about it. The brain of the project is my self-made arduino board with a WiFi Module on it which does all the notification thingy. I mentioned that the speaker is ripped out from a bluetooth speaker in the video but it actually originated from one of my really old Simon Says project which I don't remember where I got the speaker from. Anyways, it was a very compact and challenging project.