I released version 2.1 of the Simple MVVM Toolkit, which includes support for most of the features requested in this forum, as well as some bug fixes and other improvements. Check it out:
It is now compatible with VB.NET and supports validation with INotifyDataErrorInfo. There is a sample included that demonstrates validation with RIA Services and a new IsValid property on ViewModelDetailBase. There is also an IsDirty property
on ViewModelDetailBase to support dirty-checking on model entities. I added support for navigation in Windows Phone apps and included a sample app to show you how to do this. I also made the MessageBus class public for use with non-ViewModel classes.
Lastly, I improved the UIDispatcher class and made improvements to the BindingHelper and ViewModelBase classes so that UI thread dispatching behaves the same for Silverlight and WPF apps.
I uploaded the installer both to the Visual Studio Extensions Gallery and the NuGet Gallery.