Any WinRT iCommand/CommandBinding implementaiton samples out there?

Unfortunately there does not seem to be a native class that implements it for you. The interface is not overly complicated if you want to implement it yourself, and the popular MVVM Lite toolkit includes its own version of RelayCommand. You can add MVVM Lite to your project by right-clicking on References and choosing "Manage NuGet Packages". If you don't have this option, enable Nuget under Tools -> Extensions and Updates.

Check out RelayCommand class (only METRO code). The NotifyPropertyChanged class can be found here. The NotifyPropertyChanged class is only used to allow bindings on CanExecute and update it with RaiseCanExecuteChanged.

The original relay command class can be found here

My all time favorite has to be the DelegateCommand provided by the Microsoft Patterns and Practices team. It allows you to create a typed command:

MyCommand = new DelegateCommand<MyEntity>(OnExecute);
...
private void OnExecute(MyEntity entity)
{...}

It also provides a way to raise the CanExecuteChanged event (to disable/enable the command)

MyCommand.RaiseCanExecuteChanged();

Here's the code:

public class DelegateCommand<T> : ICommand
{
    private readonly Func<T, bool> _canExecuteMethod;
    private readonly Action<T> _executeMethod;

    #region Constructors

    public DelegateCommand(Action<T> executeMethod)
        : this(executeMethod, null)
    {
    }

    public DelegateCommand(Action<T> executeMethod, Func<T, bool> canExecuteMethod)
    {
        _executeMethod = executeMethod;
        _canExecuteMethod = canExecuteMethod;
    }

    #endregion Constructors

    #region ICommand Members

    public event EventHandler CanExecuteChanged;

    bool ICommand.CanExecute(object parameter)
    {
        try
        {
            return CanExecute((T)parameter);
        }
        catch { return false; }
    }

    void ICommand.Execute(object parameter)
    {
        Execute((T)parameter);
    }

    #endregion ICommand Members

    #region Public Methods

    public bool CanExecute(T parameter)
    {
        return ((_canExecuteMethod == null) || _canExecuteMethod(parameter));
    }

    public void Execute(T parameter)
    {
        if (_executeMethod != null)
        {
            _executeMethod(parameter);
        }
    }

    public void RaiseCanExecuteChanged()
    {
        OnCanExecuteChanged(EventArgs.Empty);
    }

    #endregion Public Methods

    #region Protected Methods

    protected virtual void OnCanExecuteChanged(EventArgs e)
    {
        var handler = CanExecuteChanged;
        if (handler != null)
        {
            handler(this, e);
        }
    }

    #endregion Protected Methods
}