There is a project display in my bro's school and the prize is 500$. I wanna make something cool for him which doesnt cost like 100$. Cheap yet attractive with my arduino UNO or without arduino. I already tried the lie detector/Truth meter and failed. Any cool ideas friends? 
What skills/experience/resources do you have available to you? What sort of thing interests you? Without any idea of what sort of thing you're capable of achieving with the time and money available to you, or what you would enjoy working on, it's hard to know what to suggest.
This ?
Duane B