First up is the On Beat Solar headphones, featuring a solar charger in the headband. The solar charger powers two lithium ion batteries located in the cans: plugging them into a phone charges the battery while you listen to music. The people behind it are self-funded and hope to have it in the market for around £100 ($162 US) by next March if there's enough interest.
The app listens for gunshots and removes the noise from the audio feed, so you and your friend can shoot things without interrupting your conversation. It'll be out for iPhone in the next few weeks for $10, with an Android version to follow. The mind boggles.