Samsung and the Tizen Association recently made the Tizen Software Development Kit for Wearables available from the Tizen developer web site. The SDK supports any wearable running Samsung's Tizen operating system, but that's an extremely limited number of devices at the moment, with just the Samsung Gear 2 and Gear 2 Neo smartwatches filling the space.
The InternetDJ API opens this electronic music site to your app. Since 1997 (not a typo!) composers and fans have been able to share and mix music and videos. According to the API's website, requests are limited to 5,000 a day, responses are in JSON and an auth key is required.