We live in an older home with a quaint mailbox recepticle, and unless it is overflowing, we need to inspect if we have any mail.

I wanted a way to notify us when mail was present. I am planning on using ultrasonic sensor to indicate the the presence of mail, and use a buzzer to notify us. With my other project to build a sensor network for my home, I thought I could just broadcast to that network and get alerts on my phone.