The Withings PHP library by Alexander Liljengård was written with the purpose to adapt to the body metrics' functionalities of the API. It works with OAuth1 to get measures of activity, body, intraday, and sleep. For more information about authorization, parameters, and reference, visit http://oauth.withings.com/api
Samsung isn't making it easy for developers. The company may have released a handful of SDKs for its latest devices, but Samsung's non-committal approach to its Tizen platform is probably going to cost it developer support.
You have heard of fitness apps that collect personal data. Well, now a system is in the works to quantify your car data as well. Eventually, it will make that data available in personal APIs for other developers to build on.