API for information about the network connectivity and its status

For mobile and also for other platform, it would be nice to have a single API to probe:

• the network link is connected to wifi/ethernet/mobile
• the network is present
• the internet can be reach
• maybe a specific host can be reach
• if it is mobile connection, is it in roaming mode?

Would be nice to have this is an observable way. Many application need to implement this to have an online and offline operation mode. This would be an observer pattern for the app. The app would get a signal in case of changes. Ideally this signal contains basic information about the change or the app can then retrieve detailed information.