I remember reading once that for every four minutes that a person spends in the shower, on average, one more ton of carbon dioxide gets released into the atmosphere. Carbon dioxide is a greenhouse gas, and so the time we spend in the shower in the mornings contributes to the greenhouse effect.

This isn't something that people think about at seven in the morning before they've had their morning coffee. So, I say we either invent a coffee pot that sticks to tiles with suction cups and brews coffee in the shower...

...or (better idea) invent a contraption that displays to people just how many tons of CO₂ they're releasing into the atmosphere. This could be a simple dial that just senses when the shower goes on, and a little digital readout that increments as the hot water flows.

That would put the issue on people's minds, right when and where it matters.