Ultrasonic Module HC-SR04 Distance Sensor For Arduino Part 2

My Idea
I came up with three different inventions involving the distance sensor.

Snow alarm

My father would always be late for work because he had to shovel snow. What if you could get a sensor to trigger an alarm once snow reached a certain depth? My father's alarm would wake him up earlier than usual anytime there was heavy amounts of snow on the ground.

Hide & seek cheat app

It would be like having Sonar at the palm of your hand. Your phone could detect if someone was hiding under the bed or behind a tree.

Dogs Assemble!

Dogs are known for having good hearing. My dog constantly jumps on guests whenever they arrive at the house. What if I could press a button on my phone that would trigger sound waves attached to my dog's door. My dog would run towards the sound waves. The guests in my house will believe that I have a perfectly trained pet.