#1 A penny a day, keeps a piggy happier
As money gets more, the piggy's cheek becomes redder/ piggy sounds more pleased.
#2 Floating duck
While you are taking a bath, the duck will change color with the wave. Or the duck will inform you once the water arrives certain height while you are away and keep storing hot water in the tub to avoid wasting time or water.
#3 Answering Door
Using IR sensor to release voice message from the host. Or using push button to allow visitors to leave their message to the host.
#4 No real height
This height measurement machine won't hurt anyone with telling your real. It will only tell you who else has the same height as you.
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