Some inventions could be:
System that reuses the water from your shower (provides more water, less cost)
Concussion Detector
Renewable Wave Power System (provide water energy)
An arm that can help you lift heavy stuff (helps your body stay safe)
Wind-Powered House (the way that would work is the wind hits your house and your house has sensors that transform the wind into energy to use in your home)
Gum that helps your teeth stay healthy and fixes them
Im not that good at coming up with ideas :)