A lot of people have peanut allergies.  Some people are affected by small amounts of peanut oil in foods that were just processed near peanuts.  A menu for them is a dangerous place.  Why not make a peanut detector that would sniff food and tell the owner if it had peanuts in it.

• It would have to be handheld
• easy to use
• cost less than $200

The market would be millions of them.  I suspect that there is a chemistry breakthrough required to make it happen.  And as a result there will be a very rich chemist when a detector/indicator is invented.  Right now there are lab kits and dogs that can detect peanuts in products but they don’t meet the above criteria.