Idea #1: Augmented reality/virtual reality application for designing shoes/clothes. Often times when designing any footwear or clothes, seeing the working product online or on paper is different than seeing the product being worn in person. Being able to preview how a product would appear on a person (particularly a consumer) would aid in the design process.
Idea #2: Music visualizer. Have a way to see different parts of music (e.g. bass, treble, etc.) change as a song progresses. This could be used alongside or integrated with an application like Spotify; the visual could be a display option on the desktop app or on a TV during a party.