Project for Sasco $30 dollar total

Image Example: [login to view URL] Image example 2: [login to view URL] I'm looking for someone to put together a quick circuit that will help me accomplish the simple task in the photo. It must operate on the least amount of components necessary and needs to use SMD components. The picture in the link above should help you understand exactly what I'm looking to accomplish, i know its simple but I just don't know how to get it done. I assume with transistors which I tried to understand but can't wrap my head around them. I need the output voltage line to be able to be enabled or disabled by hopefully just grounding a pin.