Make a PA system mic with sensor to track the face of the speaker. As he approaches the mic, its height will automatically be adjusted for his height.

Make bathing platform at a higher level with run off collected in a WC which could be used to flush toilet. It will save a lot of fresh water.

Many trains have toilets with open drain. When it is at platform, the muck spoils the paltform vicinity. Make a tank with vent controllable by guard or driver. He will open them only when he sees that site is suitable for dumping.

Genetically develop a plant of which every part has a use. Say roots make potatoes, leaves are spinach, flowers are a show and seeds are to eat so were the fruits.

A number of youths hook on to porno sites due to curiosity to know about body of other sex. Make a body teacher club where volunteers will be available for visitor to learn by seeing and touching body parts. This will allay his curiosity and encourage healthy interaction.